Many people have started using Google's AdSense program, but there are some who find it a bit too uncertain or simply not suiting their own requirements from an ad program.
But thankfully for such people, there are many alternatives to AdSense which attempt to alleviate some of its shortcomings. Here is a list of the most noteworthy ones from the lot with a description concerning each one.
RealContext uses Artificial intelligence to retrieve the most relevant ads for your page. And there's an extra feature which makes RealContext unique as well. Keywords are selected based upon which previous selections payed off and which didn't. That means there's a constant feedback process that ensures you gain better revenue from your ads. It also supports blocking certain adds and child-safe filtering and many more options.
Clicksor will earn you as much as 60% from the amount of money your website produces. What you get is about the same as AdSense, there are targeted text ads, you can view the revenues from your website in real time. You can receive money via PayPal or through a check every two weeks, provided that you have earned more then $50. If you haven't made that much, your earning roll over to the next period.
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.
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.
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.