My personal favorites are:
-Forecast Fox: The weather for the week right at your fingertips.
-Adblock: Surfing without BannerAds
Answers:
stumbleupon and netcraft toolbar and IE tab
Gmail notifier.
Web Developer... if you are a webmaster, this tool is invaluable....
FYI.....just for kicks, there is an ie version.
http://www.nils.org.au/ais/web/resources/toolbar/index.html
IE Tab is the best one