Chances are you're reading us (and goofing off) at work while trying to pretend you're not slacking. Spreadtweet's an easy way to check twitter while making it seem like you're a not a lousy employee.
Here's the key: it looks like Excel from Office 2003, 2007 or 2008 (Mac). All your tweets are displayed in plain text down down the page, and you tweet by typing yours in the top textbox and hitting send. There's even tabbed views along the top, making it a relatively complete Twitter package.