Greasemonkey is one of the the most popular extension for any Firefox user and every one would be looking for a Firefox 3 compatible version before they update. So here is Greasemonkey 0.8, a pre-release version for Firefox 3. This version was first spotted in this thread in Greasemonkey users group. The latest version of Greasemonkey can be downloaded directly if you are using Firefox 3.
Although there is no news from the developer, you can still use this pre-release version until a final version is released.