I just came across this, thought I'd let the DP crew know about it. It'll give you search demand for Google Adwords, and estimate Yahoo and MSN/Bing monthly demand. It's not perfect, I still prefer the Adwords keyword research tool, but this could be a nice tool for keyword discovery. Anyway, hope this helps someone. www.Spacky.com
Really nice tool, but I have seen this tool endorsed earlier also here. Btw Google adword tool I think mainly shows stats harvested from PPC campaign. Not sure if it is relevant for organic search.
nichebot is pretty kickass, but it is about 90 a month and is overkill for anyone who doesnt do this as a living.