Google has added a new feature to its infamous Google Toolbar by now allowing users to add their own custom buttons. If you are have a function in mind most likely Google has got a button for it on display in the Google button gallery. Interestingly, there are a few pages of blog toolbar button entries. According to Google the popular buttons currently are:
3. Dictionary (Google)
4. Mood Ring
5. Google Video
Of course, if you do not see a button you like you could take a crack at coding your own button.