I've used a bunch of them now. Wordtracker seems to be the most useful, but I don't want to pay the $$ if I can find something similar/useful elsewhere. I've used Aaron's tool at seobook and that's probably the best free one, but it still lacks something along the lines of Wordtracker's KEI and also (for me anyway) seems to show the same results for broad, phrase and exact matches. So I'm still I'm searching for the definitive keyword research tool. Something that will let me drill down into a niche, suggest related phrases etc., but also something that will do some sort of analysis/calculation based on search volume and competition so that keywords I have the best chance of ranking highly for will rise to the top- and is hopefully free. Is that too much to ask for?
Thanks. I'm looking for something either web based or Mac based. Guess that narrows the field a bit huh?