I would not use it. This article discusses Twitter's policy on trademarks. They generally allow "tweet" in products, that use the Twitter API. They have trademarked "tweet" but unless you are doing something wrong (scams, copying twitter interface, etc) they will let you be:
"We have applied to trademark TweetAnd they will probably send a "Cease and Desist" if the site has "Twitter" in its name. As for "Twit", it is trademarked by twit.tv.
because it is clearly attached to
Twitter from a brand perspective but
we have no intention of "going after"
the wonderful applications and
services that use the word in their
name when associated with Twitter. In
fact, we encourage the use of the
So either way with "twitt" you are going to be infringing on some trademark.
Then, there is this convention that twitter related services use "Tweet", so even if Twitter are ok with you using "twitt", there is already a site called tweetpages.com, so you might lose a fair amount of traffic when people confuse the two.
twit: n. a stupid person. (Also a termExtra reading:
of address.) : What a yuppie twit!
IANAL, but that would be up to Twitter to decide if they want to pursue it.
It would also depend on if you are competing with them.
I don't believe it would be, but, you could just check with their general counsel and see how they would react, perhaps.