Of course if there's a product, you'll expect a competitor or a similar service. I actually found a couple of them. They do not actually rival Google Adsense on your sites but they do compliment it. Some will let you run theirs with Adsense.
So we are talking about making money by placing advertisements on your site or blog. The pioneer of this is Google and now there are others that offer the same service. You earn when somebody clicks on the ad on your site and they also do target marketing. This means the ads on your site complement your site's topic or content.
You can register on this site either as a publisher or an advertiser. They also do target marketing so that the ads that will show on your site are relevant to its content. They also have a referral program which pays decently. On all buying and selling activities referred, you earn 50% of AdBrite’s profits for the first 3 months and 10% of AdBrite’s profits for the next 9 months. Isn't that cool or what. You earn both ways.
Based on my personal experience, I just started to place ads last week and within 7 days my Adbrite account has $3 total for my 3 sites. They offer a couple of ad types to suit your site. They have banner and or text ads, full page ads and in line ads. You can choose the three to apply on your site. Registering on the site is free and being a publisher is also free so why don't you take advantage of this chance to earn. Join now and earn by placing ads on your site and referring others.