I just spent an hour or so at the new keyword tool for adwords. It gives you a nice list of variants for any search term that you type in. Different from the Overture Keyword Suggestion Tool and similar to the Wordtracker related terms list. To find this tool, log into your Adwords account, click into an existing campaign, and look in the "Tools" line right above where the proof copy of your ad is displayed.

The image on the right is a querry that I ran for "sneakers". Note how it returned related terms and not simply concatenations. Great for lateral prospecting.