I use infolinks to either my sites, and I can sure that is better than Kontera. Isn't an alternative to Adsense, because I think Adsense is the best program right now. But can be used to integrate it and make additional income.
This is true that Google adsense is the best way to earn money from internet. But everybody cannot earn a lot from Google adsense. Sometimes your account may be banned for some reasons. If this happens then you may go for adsense alternative. Adbrite, Kontera or Bidvertiser may be best alternative to Google Adsense.
I have been using clicksor on a few of our sites that Adsense cannot be used on and generally i am finding them very good,dont even bother signing up for bidvertiser that was a drastic mistake for me the main reason is very small revenue earnings.
I used to use Yahoo myself for advertising. I would spend a good amount of money monthly. Maybe Yahoo publishers might be worth looking at.
Google Adsense is best . If you will try other then you may or may not get your payments on time. Adbrite and Bidvertiser is worst for me.