Bidvertiser (http://www.bidvertiser.com/)

Like AdSense, Bidvertiser displays text ads in your page. But the difference lies in the fact that advertisers bid over your advertising space, ensuring you earn as much revenue as you possibly can. This also means that bids will increase over time, earning you even more cash. You also get a great way to customize your ads with a very easy to use tool and detailed reports on your site's status.

Quigo AdSonar (http://www.quigo.com/adsonarpublishers.htm)

Quigo AdSonar achieves relevancy by placing a filter according to your site's categories. It also offers you on-line reports of your site's status and the possibility to add your own custom ads replacing ads that don't gain you any revenue. The setup is very simple, in a similar fashion to AdSense's and quite customizable as well.

Vibrant Media IntelliTXT (http://www.intellitxt.com/site/web_01a.html)

Vibrant Media IntelliTXT offers user-activated ads, highlighting certain words within the content of the page and presenting relevant ads when a user hovers his mouse over them. It uses a pay-for-performance pricing scheme and can easily be used along with other advertising methods, because it is unobtrusive. It places you in full control, allowing you to easily integrate it within your site with some simple JavaScript.

Nixie (http://www.nixxie.com/display.php?section=Partners)

Nixie claims to hold a technology that can read and understand your site, enabling it to display the most relevant content to your site. Besides text ads, Nixie also features price comparison listings as well as live auction advertising. It's very easy to implement and has a good payment policy as well.

MIVA AdRevenue Xpress (http://www.miva.com/us/content/partners/arx.asp)

MIVA AdRevenue Xpress is targeted towards small and mid-sized publishers. It implements Search Box functionality and also features things like a Category Directory as well as the handling of 404 error pages. It can be integrated with your page using a simple on-line wizard.

Fastclick (http://www.fastclick.com/publish.html)

Fastclick offers you an impressive 65 percent of what it makes from a click on your website. Payments are done monthly, via PayPal or through checks. The ads can be formatted as you wish, and Fastclick even offers a free support serice for its members and no fees are required to register with the service.

contextWeb ContextAd (http://www.contextweb.com/Corporate/publisher/publisher.shtml)

ContextAd offers the possibility of contextual ads for dynamic pages, meaning ads will change as soon as your page does. It's very easy to use and free to sing up for and offers a transparent payment policy. The ads are fully customizable and real-time reports are available 24/7.

AdBrite (http://www.adbrite.com/)

AdBrite offers publishers the possibility of integrating text ads in their pages. These are done on your own rates, with the websites you approve by hand so it bares some similarities with a classic advertising scheme. You also have the option of adding a "Your Add Here" button that buyers can immediately click to ad space on your page. It can also be used in conjunction with Google AdSense, maximizing your CTR and offering advertisers the possibility of showing their links in your Google AdSense space. You have full control over the look and feel of your adds and finally, you get an incredible 75% of what the advertiser pays for on every click.

So, as you can see there are many offers for this kind of advertising, and many hybrids based on AdSense like advertising. Also, a lot of services can work together with AdSense to earn you an even greater amount of revenue for your ad space.