I came across this interesting tool that is being offered by the US Patent and Trade Mark Office. It appears quite substantial and should be useful. The US market is usually a target for my clients, so you should give it a go and see how you stack up.
In my 12 years of practice here in Australia, I have found that many businesses are woefully ill-informed when it comes to Intellectual Property. This is dangerous, particularly when taking on foreign markets such as those of the US.