I spend a great deal of time collaborating, sharing, and commenting, both in and out of the office. That being said, I've used a lot of different browser plugins that come and go without much fanfare. Although they are usually great for a specific task (sending screenshots, posting to Facebook, adding comments), they usually aren't worth the extra browser real estate or don't work across browsers.
So I did some hunting today for a browser plugin that could bring together some of the more helpful tools without giving me a headache when I don't need them. useKit is a cross-platform, Firefox/Chrome/Safari plugin that allows you to:
All with a very neat hideable toolbar at the bottom of the browser. You can even add and remove any of these features from a simple control panel.
Here's the link to their site for a full explaination
I'd definitely check it out, especially If you've ever scared yourself off of toolbars with images like these: