Sometimes when I have many pages loaded as tabs in one Safari window, I would like to look at two of those pages at once. So I wrote an AppleScript called Load Tab in New Window (view source, download compiled script) that re-opens the frontmost tab in a new window and closes the original tab, effectively popping the page out into its own window. It's not perfect, but I find it handy.
If you need a bit more detail on the script, you can read about it here. This is somewhat similar to this hint, but much simpler.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061219120459296