Gspell is a great little add-on for Mac users to add system-wide spelling recommendations from Google search results. For 10.4 users, Tiger's had spell-checking from the New Oxford American Dictionary built in, but even that has its limits when it comes to brand-new words and company names. Gspell's solution is to search Google to find spelling recommendations based on top results. This comes in handy when typing in people's last names, or site names that are slight variations of real words, such as Digg, Yelp, and CNET.
Gspell does have a few limitations. For one, it won't work if you're not connected to the Internet. Users also have to use a three-key keyboard combination to get it to work, which casual computer users might find a little tricky. If you're anything like me though, firing up your browser to use Google for a quick spell-check is kind of a pain, which this tool makes obsolete.
The creators have made an example video, which I've embedded below.