I'm getting a major feeling of deja-vu here, but can't find why. Did I write about this earlier? Google doesn't seem to find anything, so I guess...

• Scrapbook: This extension allows you to save archives of web pages (those of you on the Mac: remember IE 5's Scrapbook feature? Yeah, is is like that .)
• Download Statusbar: I'm sure I've talked about this before, but its worth mentioning again. The built-in Downloads window takes up so much space, and this extension solves the problem by using only a little room (below every browser window).
• SessionSaver: Will restore your browser to exactly how it was when you quit it: URL locations, tabs, positions, etc.

Score one for Firefox: lots and lots of (useful) extensions to choose from. Safari has relatively few. Sometimes you need a basic browser, sometimes you just need a little more umph.