You can look online for .com domains here

http://www.typodomains.com/

it will show which are free and which are already registered, the WHois doesn't work

http://www.ovthistory.com/typos.html This one is even much better

http://www.domainingblog.com/typotool.html

stypo gives the possible traffic typo's can have $

Microsoft has released a tool to control if others were using the misspelling of others while searching the web and registered wrongtyped versions of your domainnames. Mostly those pages have just ads, searchfiles and spyware to install on your machine.

http://research.microsoft.com/URLTracer/

When a user visits a Web site, her browser may be instructed to visit other third-party domains without her knowledge. Some of these third-party domains raise security, privacy, and safety concerns. The Strider URL Tracer, available for download, is a tool that reveals these third-party domains, and it includes a Typo-Patrol feature that generates and scans sites that capitalize on inadvertent URL misspellings, a process known as typo-squatting. The tool also enables parents to block typo-squatting domains that serve adult ads on typos of children's Web sites

and how they work is explained here

http://research.microsoft.com/Typo%2DPatrol/ if you have trouble dowloading, this is a functional http download link

http://ftpclubic10.clubic.com/temp-clubic-rx624/logiciel/msr-strider-url-tracer_msr_strider_url_tracer_1.0.1.0_anglais_19583.msi

you will need IE 6.0 (www.windowsupdate.com) and not IE 7 beta and you will also need .net installed (automatic link opens and in xp there is no restart necessary).

Than you will have to take a safe computer (preferably one that you only use for such tasks if you are working with confidential data) and visit the sites. Take a screenshot (for example with screenhunter http://www.snapfiles.com/get/screenhunter.html

If the site has only advertising or porn or has no legal reason of being there (or in the worst case is a copy of your own site) than you have to do a whois

My preferred one is the one from www.geektools.be or for the belgians www.dns.be With this data you can also add a spyware check (for example with search and destroy http://www.snapfiles.com/reviews/Spybot_-_Search_and_Destroy/spybot.html

and to be sure you can use these tools to look for more info

http://www.domaintools.com/reverse-ip/ and more http://centralops.net/co/ and http://www.samspade.org/

And with all these facts you ask the owner of the domain space (.be for belgium etc...) to transfer or block the domains.

DomainSpa.com developed self-optimizing and traffic learning Domain Parking System that will analyze and auto optimize domain page and targeted keywords. Our self-optimizing system knows how to recognize expired or type-in domain traffic and adjust itself accordingly. Virtually everybody can benefit from DomainSpa.com's intelligent and unique Free Domain Parking Service

http://toolbar.domainspa.com/10/

Their toolbar has a typomizer Do you receive all potential traffic to your own website? Website surfers tend to make errors. Enter your own URL and evaluate many potential misspellings that could bring more traffic to your site.