If you're looking for a way to wring a few more bucks out of your blog each month, you might consider giving Text Link Ads a whirl. Until recently their system wasn't compatible with Blogger but that's changed in the last few weeks, and as long as you're using the new fancy Blogger version (or upgrade to it), you can install Text Link Ads and start making some extra scratch each month. (Unless you have an old, large blog, like this one, which you can't yet switch over to the new Blogger platform.)
Signing up for Text Link Ads is pain-free and they give you control over how many ads you'd like to sell on your site, what they look like, all that good stuff. They'll also give you an initial instant estimate of what they think you'll make each month, based on a quick analysis of your site. You install a bit of code in your blog, Text Link Ads automatically finds it, then gives you a thumbs up and starts trying to sell the spots on your site to their base of advertisers.
Pretty simple and painless and I've made decent money on other sites of mine using them. The ads also aren't insanely annoying, as they're simple text ads with no graphics or any other hoo-ha. They pay you the first of each month by check or PayPal for the ads sold the previous month. The income won't make you rich but they're a nice source of extra cash that requires very little work on your part.