I definitely recommend FireBug. It is, as the article states, a dream extension for Firefox. After it becomes second nature to use, you'll wonder how you got by without it. (Probably quite fine, but the app is great!)

ClickTale should be in any new startup's arsenal. Saves the need for expensive, old-school usability testing.

Do you use any of these tools? I used basecamp before and I would like to add oDesk to the list

I use Firebug too and love it

Great List; Thanks Brian!