I just setup the Roundcube webmail client on my server. It's written in PHP, but it's so good that I need to share it with the rest of everyone here. It took me about half an hour to setup, but then my jaw dropped. This is the best webmail client I've seen, bar none. I highly encourage you to check it out. Drag and drop message manipulation, Ajax, DHTML, these developers got it right in a fantastic way.
