Froyo rooten the easy way (update).

The bad news: the Wifi exploit described below has been fixed :(. The good news: an even easier exploit has been found :hat::drunk::hat:.

The exploit has been described on the Nexus-One Forum. And for those who don't like to copy dozens of commands into a terminal xda-developers has a one click rooter app. You will need to register a user for both of them to download the needed files.