Gmail - Windows Mobile, iPhone Push and a Contact Picker

Not only in the lab but outside, too; not just for a small subset of users but for everybody: Gmail keeps piling capabilities and convenience.
You can now choose recipients from your address book, for example, and add Gmail as an Exchange account to Windows Mobile and iPhone (including message pushing). The iPhone web interface, in turn, learns to move messages.
On larger but still small screens, you can remove labels from the message list to make room for subjects. Speaking of concealment: with the right flask from the lab, labels with no unread messages move out of the way automatically:
›› Gmail is the Google approach to email and chat. Practically unlimited free online storage allows you to collect all your messages, and Gmail's simple but very smart interface lets you find them precisely and see them in context without effort.