Here's a nifty feature of the recently-released Twitter for Mac. It adds a contextual menu option to Mac OS X 10.6.6 for super-easy tweeting. Just highlight a bit of text, right-click (or Control-click if that is your wont) and select "Tweet" from the contextual options. Twitter for Mac will produce a compose window with your selected text intact.
We've found that it works in Safari, Chrome, iCal, OmniFocus, TextMate ... pretty much any Cocoa app that supports contextual menus (but not Microsoft Office apps). It's certainly convenient, especially for those for whom copy-and-paste is just too much work. Check it out and enjoy contextual-tweeting.