I've been using Dave Winer's Flickr-to-Twitter for a few months now.
Using Dave's software, I take a photo with my iPhone or Curve, email it to flickr, and it automatically posts to Twitter with the name of the photo and the url. It works simply and perfectly.
It's one of my favorite uses of Twitter & flickr. Sharing a photo "in the moment". But it is been a closed service and unavailable to the general public.
If you use Flickr and haven't tried Twitter than I bet this will get you twittering away.