I do a lot of keyword research online, and even though I use a couple paid options I am always looking for new ways to come up with results for the niche products and sites I create. I have compiled a list of all the sites I tend to visit from time to time and thought maybe other marketers would be able to use it for their keyword research.
FREE Keyword Tools:
Lycos own list of the 50 most searched keywords
http://50.lycos.com/
Search funnels with Microsoft. Here you input a keyword and choose if you want to get results that starts with the word your are searching for or ending with that word.
http://adlab.microsoft.com/searchfunnel/
Great domain searcher that lets you type your word while it checks the availability, but only for.com and.net
http://www.ajaxwhois.com/