I've been using the Chrome/Chromium Teambox extension for a while and I thought in some changes that makes it more useful to me.
The developer of this extension has done a good job and a good start for adding more features in the future. Actually Teambox Notifier shows your last activity entries such as tasks, conversations, etc.
I found it useful, but I thought it could be better for my needs with some simple functionality. First I'm thinking about putting a selector in all tasks in the activities list and make a put request to change the state of a task so you don't have to enter in Teambox site to do it.
You'll be able of following my progress (bad or good) at github.com. :-)