Twitter's Web site is being run over by hackers exploiting a mouseover flaw.
Sophos has detailed the flaw and recommends that you use third party software to Tweet. Indeed, I found out the hard way that Twitter's site is a mess right now.
We'll see. In the meantime, don't bother with Twitter.com. No user interaction is required. Simply put, you'll get something like this:
Update: Twitter has patched the flaw.