As mentioned in the opening section, an advertising marketplace will only work when you have a good volume of traffic on your blog. So make sure you have it before registering on these ad platforms.Let's get started and check out these direct advertising marketplaces built specifically for professional and niche bloggers. I've used some of them and the results were promising, right from day one.
BuySellAds: It's one of the most popular advertising marketplaces for publishers. Some of the most popular niche blogs use its services and earn thousands of dollars per month. They take 25% of each ad sale for their service. Finding advertisers, bookkeeping, ad-hosting, and payments are all maintained by BSA.
OpenX Ad Exchange: OpenX is a popular ad-serving solution quite popular among publishers across the globe. Its ad marketplace gives you an opportunity to showcase prime space on your website or blog for potential advertisers. The bidding and payment process is transparently powered by a rock-solid OpenX ad-serving engine.
AdSella: It's yet another direct advertising service that acts as a middleman between an advertiser and a publisher. You can sign up for a free AdSella account and can start earning money by grabbing ad deals from their ad marketplace. AdSella keeps a percentage of ad sales as a fee for their service. Payment is done on a weekly basis through PayPal.
adMarketplace: It's a premium advertising marketplace for publishers with more than 10,000 advertisers including some big names like Dell and Comcast. You must own a blog with decent traffic devoid of any crappy content to get any advertising deal from adMarketplace. Bidding is done for CPC ads on performance-based data. The more deals you grab, the more good ratings you get.
Chase Clicks: As a publisher, you can choose two different types of advertising opportunities through 'Chase Clicks'. You can sign up either for CPC ads or for CPA ads. There are thousands of advertisers in both categories offering premium rates for deserving high-traffic blogs and websites. 
Primis: With thousands of advertisers, Sekindo is yet another popular advertising marketplace for web publishers to do video monetization. Simply sign up for a free account and paste ad code on your blog to start earning from day one. The payment system is flexible and transparent with lots of ad formats and configuration possibilities.
Gourmet Ads: If you're a food blogger, this advertising marketplace is made just for you. With tons of advertising opportunities, you can make your food blog a hub for the food and hospitality industry. Gourmet Ads offers flexible and lucrative CPM-based ad opportunities for publishers. Large 300x600 ad formats yield high CTR giving you more advertising deals again and again.
SmartyAds: This ad platform is best suited for programmers and website owners who're technically sound. You can use this powerful solution to integrate ads with different types of applications and devices. With plenty of ad networks to choose from, you're in good company. Do try it once for your application.
AdView: This advertising platform excels in mobile advertising. If your website or an app receives tons of mobile traffic, sign up for this one and witness your earnings soaring towards the sky. You get diverse ad formats and a rich reporting dashboard to get the best out of this solution.
Clickadu: And last but not least is this excellent ad marketplace offering a diverse range of monetization solutions for the publishers. You need to have at least a traffic of 1000 unique visitors per day to use this advertising platform. With flexible payment methods and high eCPM rates, you're in good company.