Everybody should take a serious look at DigitalPoint's Coop Advertising Network at http://www.reversi.se/adnetwork.php
In exchange for one dynamic text link in your header or footer, you get your keyword display across the entire network... and the best thing is that you can change your keyword and description at any point and it will be reflected throughout the network!
I was stuck betweek #19-25 in the serps for about a month, and was taken to #6 without any other changes than the textlink in the footer