I find that having the 'Add to del.icio.us' bookmarklet in my bookmarks bar and then just hitting Cmd+1 whenever I want to bookmark something works pretty well.

I tend to hide the bookmarks bar because the way I use it, it just takes up unnecessary screen space, but the procedure above doesn't require it.

Those two and AdBlock---though I just discovered an ad blocker on pimpmysafari.com. (For the record: I use Firefox.)

Check out safariadblock (safariadblock.sourceforge.net) for an adblocker that is basically a port of adblockplus.