… should probably take heed of my own advice above (its Welsh—I'm Welsh!), but its never stopped me yet ...
Here’s an extension a lot of people have been waiting for: it automatically restores your previous browsing session.
At the moment, the MIME-type is set incorrectly on the extension itself; instead of clicking on it, right-click the link and choose “Save Linked File As…”, then double-click it in Finder (or in Explorer, for Windows users) to install it.
Few glitches with v1.0 (ie/ ignoring multiple windows at restore), but looking good as one of a raft of replacements for Glims functionality in the older Safari 4 world.