Safari Extensions is a Tumblog for extensions for the newly released Safari 5 (which now supports extensions).
As a bonus, I found from this reddit story that the shortcut key to 'undo close tab' is cmd-z. Technically this makes sense (ctrl-z being undo) but the other two major browsers (chrome and firefox) use ctrl-shift-t to do this, so it would have been nice. Also it doesn't seem to undo multiple tab closes, which would be nice as well.