I can recommend a fabulous AdServer system... it's called phpAdsNew and it can be found here > www.phpadsnew.com
If you want to see it in action I use it to present the banners you see at the top of my main domain www.themouthpiece.com and am successfully generating revenue using it. I am about to implement a time based banner campaign as well as the current page request rotation campaign. It is packed with features and I even managed to install it to the same MySQL database as my phpBB forum and osC app.... all off one MySQL database...
I can't offer much advice to anyone here on osComemrce just yet as I am still learning about it myself, but I suppose it's a small return of favour to anyone who might require assistance with phpAdsNew...
Maybe I shall be told off by one of our Mods for offering support on another product, apologies but so be it...... if you want help, PM or email me...
John