This sounds like it would have loads of support in that we're all out to make a bit of money with our blogs but, so far, it isn't really.
There is Adsense Deluxe which does most of the work but leaves you to edit each post to put the advert in yourself. Anyway, I've far too many posts to be doing that so I've run up a little plugin which works in conjunction with Adsense Deluxe to add adsense (or similar) adverts to your posts.
Installation:
1. Download Adsense Deluxe and install as instructed.
2. Add your adsense block as below (change the publisher ID to your own, unless you want to be generous to me):
<div style=display:block;float:right;margin: 0px 10px 0px 0px;>
<script type="text/javascript"><!--
google_ad_client = "pub-7998730676696046";
google_ad_width = 336;
google_ad_height = 280;
google_ad_format = "336x280_as";
google_ad_type = "text_image";
google_ad_channel ="4549167711";
google_color_border = "CAF99B";
google_color_bg = "CAF99B";
google_color_link = "000000";
google_color_text = "000000";
google_color_url = "0066CC";
//--></script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script></div>
3. Note the two div tags before and after the adsense code.
4. Download Add Headings, rename it to add-headings.php then activate the plugin.
5. Go to the options screen on your Wordpress installation and add:
<!--adsense-->
as your heading.
And that's it!