ForgetMeNot... When I use Safari, I like to keep a lot of tabs open; but when I close Safari, it forgets what I had open. Consequently, I wrote ForgetMeNot - a SIMBL plugin for Safari which saves the URLs you were visiting when Safari quits, and reloads those same websites for you when you start Safari again. ForgetMeNot also adds an "unclose window" option to the file menu, and an "undo close tab" option to the edit menu.
Version 4.2 of ForgetMeNot works with the current version of Safari, namely Safari 3.1.2.
Safari 3 or later