Nowadays, with social media and branding being so important to a company's image, it is crucial to have a presence on some of the more popular websites out there.
The application is surprisingly fast and fun to watch it go through each site and scour them for your chosen username.
Having a presence and active profile on these sites can help your Search Engine Optimization, and get the word out.
Now, mind you, not all of them are important in a business sense, and some of them are not even around any more, but some of the notable ones are behance.net, Blogger, Flickr, FriendFeed, Twitter, Xing, and maybe even YouTube.
Check it out at namechk.com