Wordtracker is obviously the best KW research tool and I've also heard some really good reviews about Keyword Discovery.
the best keyword research tool is crap unless you use two or three at the same time. This will help https://adwords.google.com/select/KeywordToolExternal (tells you how much keywords are worth and the competitors) http://freekeywords.wordtracker.com/ (tracks searches) http://www.google.com (good for searching once you are considering a certain keyword. It'll tell you what's up with who's the competitors, and if you think you can beat those ENEMIES)
i use overture plus this tool http://conversion.7search.com/scripts/advertisertools/keywordsuggestion.aspx
I know one, it's http://inventory.overture.com/d/searchinventory/suggestion/ But this service is really slow and it often don't work. Thanks for you suggestions, now I know some normal keyword research tools.
Here's some suggestions: Ways to Find Your PPC Niche (Adsense, etc) Also, Google has a newly modified Keyword Tool in this DP thread.