Blog/Web/etc search engine Icerocket has a new tool out that’s currently in very basic early release. You can tell because there is no design about the site whatever; it’s just a Web form. The new tool, Twitcom, looks at up to four Twitterers and tells you which followers they have in common. You can try it at http://www.icerocket.com/twitcom.

It’s as simple to use as I described it; enter in the names of up to four Twitter accounts. Twitcom will thing about it a minute and then give you a list of the followers those accounts have in common.

I wanted to start with two pretty famous Twitterers so I did a search to see what followers @johncleese and @the_real_shaq have in common. Twitcom told me none. Okay, how about @johncleese and @librarycongress? Twitcom gave me a list of 1752 people, showing me their icon, number of followers, and name. (If you hold your mouse over the person’s listing you’ll also get their bio information too.) Twitter names are linked directly to Twitter accounts.

I saw that some follower lists also had “friend” lists — I’m guessing those are people who are both following the accounts and are being followed in turn. They have the same information as the regular follower lists.

When I first started playing with Twitcom I thought about it in its potential as both a toy and as the subject of a little sport at the local watering hole. (“I’ll bet you a beer that nobody is following both Laurie Anderson and the National Rifle Association.”)

But then I thought about it and decided it could have other uses, too, like for finding communities. Who’s following both @nasa and @astronomymag? Who’s interested in both @librarycongress and @ubuntugeek? Bookish people, open source people, perhaps people I would like to follow. The trick is finding interesting-but-not-ubiquitous Twitters who have some overlap, but it’s a trick I’d like to master. I’ll be playing with this tool some more.