OpenX is an open source ad server that you can install on a web server to provide a complete ad management package for your web sites. The software lets you create entries for advertisers, ad zones, and campaigns. You can also apply a whole slew of filters that will do things like show one ad to a visitor in the US and another ad in the same spot to a visitor from Germany.

The down side? Up until recently you could only use OpenX by setting it up on your web host. In other words, even if you have a web site hosted on a free service like Google's Bloggger, you still need to sign up for a web hosting account, which usually costs money, to use OpenX.

Earlier this year OpenX announced it would launch hosted version of its ad server. The service is still in private beta, but I got a chance to check it out over the weekend, and it's pretty slick. The hosted version of OpenX provides all the same features you'd get from the self-hosted version. But there's no setup required. You just request an invitation and wait (im)patiently for one to arrive in your inbox. Once you're in, you can start creating campaigns in a matter of seconds.

OpenX also recently launched the OpenX Market Alpha, which allows publishers to sell their ad space directly to advertisers. The Market is still pretty new, so there aren't a lot of advertisers just yet. You probably won't get rich by signing up during the Alpha. But it probably won't hurt either. Publishers can set a minimum rate so that your default ads, say Google AdSense, or Amazon Affiliate units will show up unless an advertiser meets that price. But if a member of the OpenX Market has a higher bid than your minimum, their ad will be shown instead.

Google recently rolled out its own hosted ad management service. But while Google Ad Manager is certainly much simpler to use, it doesn't offer nearly as many customization options as OpenX.