IE Tester is awesome (v0.4.6 as of 11-4-10): http://is.gd/gMWpJ #debug #browser #useful
RT @nettuts The 30 CSS Selectors you Must Memorize - http://bit.ly/d81xNN #useful Some nutty, off the wall selectors there.
#HotTip: If you are developing something (add on, plugin, etc), let the user do the styling—not you! Only style to make it function.