via Finer Things in Web:
Like the unofficial Gmail bookmarklets, you can now bookmark the ‘compose new message’ window of MobileMe Mail. As long as you’re logged in, visiting the link above will create a new composition window with all the contact auto-complete and rich text editing tools you need.
Strangely, while sending a message from this window seems to work, the window does not appear to display proper feedback. Clicking the send button will display a typical Mac OS X “spinner” progress UI and a “Sending…” message, and even though sending works, that progress UI never changes. Hopefully, the MobileMe team can fix this UI quirk and keep this convenient way to send messages.