gestures is a must... right click while moving mouse up = new tab right click n down = new window... i know theres many more but those two alone save me so much time.
I like the forcast one, it lets me know whats going on outside so I dont have to >_>. Whatever you do, don't get the one where it shows the download in your taskbar, I find it to be just very annoying because it causes your "downloads" dialog box not to show up, even after uninstalling it (the reason I uninstalled it for).
