Originally Posted by Markul

If you are a buyer, you need to check them all out - see who has the traffic that converts.

Plugrush is a good choice, but works a little differently. You need to create plugs that are displayed on publishers websites. I presume that you know you need to match the plug to what people expect to see on the landing page and all that. Here are some alternatives to PlugRush:

Ero-Advertising
ExoClick
AVA Traffic

If you really want to get your hands dirty, you should try out JuicyAds where I recommend you hand pick the sites and ad-zones on those sites. Then compare how your creatives perform.

Good luck.