Do you use an ad network on your site?

And if so - which one?

As much as I hate ads, I'm considering using one for a project. I was denied from Google Ad Sense, I'm assuming because it's an AJS 1 site and their bots can't scrape it for content, and I couldn't find any way to contact them and dispute it.

So what network do you use and what kind of success have you had with it?