[kylef]

Apple - Safari - Safari Extensions Gallery

A Cleaner YouTube is pretty good, as is Google Search Cleanup if you don't use the paid-for Adwords on the right hand side.

[Cold Warrior]

I like Ultimate Status bar. Let's me reclaim some pixels at the bottom, but get status bar info on demand. Simple but effective. Does more than that, cool stuff. Home - Ultimate Status Bar: Safari Extension

[Brien]

Originally Posted by Cold Warrior 

I like Ultimate Status bar. Let's me reclaim some pixels at the bottom, but get status bar info on demand. Simple but effective. Does more than that, cool stuff. Home - Ultimate Status Bar: Safari Extension

I've been using Invisible status bar. I like it better.

[Curiosity]

I like Safari Stand and Safari Block. Safari Block blocks ads. In fact, it has a subscription to Easylist like Adblock Plus for Firefox, and you can also add your own personal block list to it. Safari Stand allows you to prevent plugin items from loading, and then load them individually later if you wish, sort of like Flashblock for Firefox. The only thing is, it blocks other plugins besides Flash. Safari Stand can also block favicons, which I really dislike, disable resizing of the window, stop junk messages from being printed in the status bar, and has several other options.

[gradient]

IMDB Links is super ugly but super handy.

[kylef]

I'm really liking the Chrome port of Adblock to Safari. If it missed any ads in its lists, right click and block.