identi.ca qwip.it prez.be tcrn.ch isup.me pbj.ca cli.gs
zi.ma bit.ly ****** ad.vu tr.im 3.ly u.nu re.p.ly
all seem to think there's some value.
Having a .com might have a slight SEO advantage over other .TLDs but unless it's in a very competetive niche it isn't that big a deal. Even if it is competitive all it means is that you have to make a little more effort than the other guys.
Back in the day a .com meant a lot for your visitors because it gave an impression that your website was more credible. Plus it was the most common tld that peopl would remember if they type in the url in the address bar. To a large extent that impression has lingered on but it's changing rapidly. Most people just click links anyway, but even when they do type them in directly it's pretty common now-a-days to remember urls with many different tlds.
The domain speculators made a big deal about buying up the last of the 3 and 4 letter .com names a few years back. In spite of their insistence on how valuable they are, most of them are still in the hands of the speculators. It's turned out that no one really cares.
If you have a need for a short url then you'd be better off using the letters you want in a different tld than you would by paying a premium for the .com version. In many cases the tld can even help make a word from your 3 or 4 letters.
The main thing you want to do though is make sure its a common tld thats beng used as a global tld. Aside from .com .org .net .gov .edu .info and .biz all the other tlds are individual country local tlds. Over the years though many of those countries have sold and promoted the tld for global use and the search engines understand that. If your going to use a countrycode tld for global use then you want to make sure it's one that the SEs are used to dealing with as such. .tv .me .ca are a few examples.
You do need to remember though that they still are local tlds though so may require a little more work to rank globally, but it can still be done.
