Although there are hundred of programs out there that promise you will make money using them on your blog; I have found that few are worth your time. Here are some I have tried and can recommend.
1) Social Spark is one of them I recommend the most. Register your blog and if companies are interested they will contact you with an offer. You can turn down any offer. Each post pays a different amount and it is negotiable. It is very easy to use and not a scam. I've have successfully used Social Spark.
2) Blogsvertise This program is the same as social spark. Register your blog and an advertiser will contact you if they want to pay you to post about something. You can accept or reject the ad.
LinkShare - I have used this in the past, but currently I am not running any ads from them. I have nothing negative to say about them and there is no particular reason I am no using them at the moment. The one ad I did run in the past with them was a Lego ad. Join LinkShare Today! You can sign up for an account and browse through the companies available through them.
4) Savvy Source - Savvy Source is another website I have used. They have many cities they offer daily deals in. You can sign up for an account and get a ad widget for your blog. If anyone purchases something through it you get a small percentage. I have run this ad in the past, but not currently. I know of a few bloggers that have made $100 or more a month using Savvy Source.
5) JuiceBoxJungle has an ad network that you can participate in. You place widgets like this one shown and you get a 50% ad split with them. This is another type of ad that I know some bloggers are making $100 a month or more from.
6) Commission Junction is another ad network that has lots of different companies you can choose from. I have been trying their ads for a while, but have yet to make any money off of them. That is where I got the Travelocity and Priceline ads. They charge you fees to work with them, which they take out of any revenue you make.