I've always wished Safari could force all windows to open up in tabs. But when I wake up from my web surfing and look around, I mananage to have more than one Safari window open. I've heard SafariStand and Saft will correct this ... but I have my doubts, and so came up with my own solution.
I've written this AppleScript that takes all Safari windows, and opens them up in one window in different tabs. Enjoy!
[robg adds: This worked well in my testing...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070204164356478