http://www.westla.net/domain-names/
This search engine isn't limited to domain names, so you can use it to find
out if your business, or perhaps a product you are developing might have a
trademark issue.
Some sites charge big bucks to enter names into this search engine for you,
but we don't operate like that! You can go there yourself and plug in the
names for free! It's a free public service, funded with US tax dollars, so
why should you pay someone for this information? Even if you're not a US
taxpayer, so what? Have a FREE search, courtesy of Uncle Sam!