Here is a great list of companies offering CPM ads: http://www.yieldmanager.com/ ** http://www.fastclick.net/ ** http://www.euroclick.com/ http://targetpoint.com/ http://valueclick.com/ http://tribalfusion.com/ http://falkag.de/ http://belnk.com/ http://bannerconnect.net/network/ http://cpxinteractive.com/ http://www.casalemedia.com/ http://www.addynamix.com/ http://www.tradedoubler.com/ http://www.doubleclick.com/ http://www.realtechnetwork.com/ http://mediaprecision.net/ http://attune.com/
If your site has a decent PR (not that PR really matters), you can try selling text links on various venues (e.g. DP, link brokers, etc). I've had some success with text-link-ads.com.