I announced here that I had updated MiddleClickClose to work with Safari 3.1, but that it had problems loading under Safari 3.0. Actually, the problem was that it wouldn’t load on a PPC chip; I was testing on my iBook G4, but I hadn’t generated a universal binary. That was caused by having the iPhone SDK installed. Anyway, I dropped back to Xcode 3.0 and got a universal binary built, and now everything is happy.
If you want the plugin, ensure you have SIMBL installed, download the binary package below, and unzip it in ~/Library/Application Support/SIMBL/Plugins and restart Safari.
As usual, it’s distributed under the GPL.