There are lots of ways that you can do this. I know of many bloggers who have used PayPerPost, Blogvertive, TextLinkAds, etc. on their sites to earn extra income from their blogs. Of course Google Adsense is everywhere you look. Nearly everyone I know has Google Adsense on their pages.
Just recently I came across another site, called TNX and I am checking into them further, but from what I understand from talking to others the advertising links are very natural looking, and they have an affiliate program as well. Although I have signed up for an account, I haven't tried it out yet because I am still checking into a few details so that I am certain I don't break any rules with Google or anything. From what I have seen so far, It looks like it will be ok to use this along with Google Adsense though. This is a direct quote from their website:
Can I combine TNX ads with Google AdSense or any other ad broker?
Answer: Yes, you can combine TNX ads with any other advertising sponsor. Your visitors will see TNX ads as direct links (usually subject oriented) to other sites. Even if some context advertising system does not allow combining ads with similar systems, you would still be able to add our code to your pages, because TNX is not context oriented and nobody can stop you from placing a direct link to another site. The HTML code of our ads is not different from a regular link.
I also know that Google frowns on selling paid text links, but TNX ads are supposed to be so natural and fit in so well with your content that even Google isn't supposed to be able to tell whether or not they are paid links or regular ones. Anyway, here is the link so you can check it out for yourself. If you have tried it, let me know what you think. Otherwise, I will be posting more once I have tried it...
TNX.net: Sell links on every page of your site to thousands of advertisers!
