i notice for somedays lot of pplz promoting widgetbucks may b because of their 25$ for joining offer soo they can b strong competitor of adsense
When it comes to contexual ads, adsense is the current reigning king. If your talking other type of ads, like CPM, I would suggest companies like ValueClick Media, Tribal Fusion, Casale Media, etc. Some websites would make more money getting paid CPM then CPC/CPA. (my 2 cents)