With such a large Android user base, countless Android variants are available for hundreds of devices that can be used to try out new innovative features and functionalities. The best way to do that is to install a custom Android ROM on your device. A custom ROM in this context is simply a modified version of the Android operating system with tons of features, apps, and themes. There are dozens of custom ROMs available for Android platform, but only a handful of them are good enough for popular smartphones. The following custom ROMs are some of the best from the entire lot and are quite popular among users. You can easily use them with most Android smartphones without any issue. If you're an Android enthusiast who loves to try new 
CyanogenMod - It is one of the most popular custom ROMs available for Android devices. It's open source and is supported, developed and maintained by large numbers of independent developers. All the versions of this popular custom ROM are based on the Android versions released by Google. Following are the some of the cool features supported by this custom ROM distribution.Rich theme support - Most smartphone users switch to a custom ROM solely because of the availability of excellent theme customizing features. CyanogenMod natively includes a powerful theme engine that lets you install and customize countless themes of your choice. Entire theme management is quite easy and intuitive.
Integrated FLAC audio codec - Popular audio encoding-decoding software stack FLAC is deeply integrated with this ROM distribution. This not only enables you to cherish your favorite music in a seamless manner, it also saves your storage space and CPU consumption on your Android device.
Feature-packed OpenVPN client - This is one of my favorite features found in this ROM distribution. Through it, you can securely connect, transfer data and can communicate across the globe without leaving any traces. Frequent travelers and business users will find this powerful feature extremely useful and handy.
Supports all popular smartphones - If you've purchased a popular branded Android smartphone, you can easily use this custom ROM distribution on it. CyanogenMod is available for a large array of Android devices which makes it so popular among the users.
CPU overclocking support - If you frequently multitask and play rich games on your Android device then you can take advantage of CPU overclocking feature of this custom ROM. This will ensure that your Android device is responsive even when multiple applications are running at a given time.
Chameleon OS - This is yet another popular custom ROM for Android users which is based on CyanogenMod base ROM. Needless to say, this custom ROM is also open source and users as well as developers can contribute to refining the distribution. Following are some of the best and powerful features found in this stable, secure and excellent custom Android ROM.Flexible theme engine - Its powerful theme management system lets you mix two different themes to create your own unique theme version. This literally enables you to create almost infinite themes from a collection of existing themes. You can also preview themes before installing them on your device.
Apps permission management - It has a flexible and secure apps permission management system that ensures that no application can access sensitive locations on your smartphone. This greatly enhances the security of your device relieving you from malicious activities of apps installed from unknown sources or third parties.
Intuitive status bar - It has a highly customizable status bar that can be configured for compact and page views. You can also enable enhanced audio controls in page view mode if you regularly play music throughout the day. It also enables you to know the status of apps in full screen mode by simply tapping the edges of your smartphone's screen.
Customizable gestures - This is one of the unique features of this popular custom ROM. This feature lets you assign custom gestures like pinch and spread to individual apps and widgets for a more personalized experience. Assigning these custom gestures is extremely easy and you can revert back to original app touch support anytime.
AOKP - This custom ROM distribution is ideal for high end Android devices though other devices can also use it. It's lightweight yet extremely flexible and powerful with several unique features. It can be used on large numbers of Android smartphones even if the system RAM is bit low. Following are some of its popular and extremely useful features.Handy navigation ring - This is a custom shortcut section to start apps or to complete an action quickly. You can add up to 5 shortcuts for apps or custom actions within this navigation ring to quickly launch your favorite applications. Users generally assign shortcuts to their daily-usage apps to quickly start them without any hassle.
Flexible custom toggles - Through this feature, you can not only change the way your toggles are displayed, but can also create your very own unique custom toggles. This facilitates quick and convenient navigation across folders and apps. You can assign these custom toggles to frequently used applications to save your precious time.
Intuitive LED control - Its useful LED notification is used for relaying status of apps and actions. You can customize these LED notifications and can associate them with a custom action. This will help you instantly recognize the completion of a specific action by a simple glance at the custom LED notification.
Custom vibration patterns - Generally, smartphone users prefer to switch off vibrations. But this feature will persuade you to use them. You can assign custom vibration patterns and can assign them to specific entries in your phone book. This way, you can identify the caller simply by the vibration pattern.
MIUI - This is a closed source custom ROM for Android smartphones and supports dozens of popular brands. It can also be run smoothly on several Android tablets. Some parts of this popular custom ROM are open source and can be modified by developers quite easily. Let's see the features offered by this yet another impressive custom ROM.Enhanced dialing pad - Unlike regular dialing pads, this one shows matching contacts from your address book while you're typing the number. It happens dynamically so you can instantly select the right number to speed up the entire dialing process.
Rich music gallery application - If you regularly store, browse and transfer music on your Android smartphone, this gallery app will save you lot of time. Its entire music navigation system and the interface is extremely user-friendly with several useful options.
Rich icons library - This custom ROM has one of the largest databases of interface icons that gives you an option to stylize and enhance the navigation and interface quite easily. It supports icons of various popular brands like iOS, Windows phone and of course Android. You can mix and match various icons collections with an active theme to create unique interfaces.
Fast performance - Soon after installing this custom ROM, the first thing that you'll notice is the increase in speed. It's packed with tons of features but surprisingly is very fast and responsive. You can further tweak it to quickly make it blazing fast that can outperform all other major custom ROMs.
Flashing and Rooting Custom ROMs
Finding a good custom Android ROM is half the work done. Generally, users are unaware of using these custom ROMs in an easy way on their Android devices. One needs specialized software to get the job done. That's where ROM managing software comes handy.Android ROM Manager - You can use this powerful Android app to install and use custom ROMs on your smartphone. It's easy-to-use and provides user-friendly options to help you manage multiple custom ROMs within a single device. Here are some of its excellent features.
- ROM backups and restore - This is one of the most critical features every ROM manager must support. If you're rooting and testing several ROMs on your device, this powerful feature will let you take backups and restore to an earlier state with a click of a button. This way you can easily revert back to stock ROM originally installed on your smartphone.
- ROM installation from SD card - Often users install custom ROM through a memory card instead of directly fetching it from the internet. This flexible ROM manager lets you install a custom ROM directly from a memory card. This speeds up the installation process and also saves storage space on your device.
- Installation through gorgeous UI - And last but not the least is an important feature that's the foundation of any ROM manager. Instead of complex cryptic steps, this app lets you install a custom ROM in a few simple steps through a user-friendly and stunning interface. Users with limited technical knowledge can also install custom ROM through its interface.