With increasing popularity of Flattr (114,057 € has gone through the Flattr system in two months), several people start to recommend what things to flattr. I'm not going into this business, however they seem so find interesting things for me so you might like it as well.
The Flattr Free and Open Source Software by Raphaël Hertzog is actually thing which has attracted me to the Flattr. It collects recommendations how to tag your free software on Flattr and each month it publishes five recommendations which projects to flattr.
The other thing I've noticed is list made each month by Evgeni Golov, which I've mostly noticed because increasing popularity of phpMyAdmin on Flattr, because he was really fast in advertising it :-).