Hi Adam
Here are a list of keyword tools/techniques I use for our keyword research
Google trends - monitor seasonal trends for certain search terms throughout the year
Competition sites - check out your competitors within your sector/subject areas - It's amazing how many large sites still incorporate defined keywords that appear in the meta keywords section of the site!
Hitwise - If you have enough luck/big enough budget to access this tool - this can unearth a goldmine of keywords to target as well as their clickstream report of what keywords/search terms were used before and after leaving your site
Google insights - provides alternative keywords to consider based on the keywords you add
Open Site Explorer - enter your competitor site and run an anchor text report - what key terms are included
Competitor blog sites - analyse your competitor blog sites - usually packed full of keywords they are trying to rank for that is used to point back to their main site
Analytics - Your existing analytics tool should provide you with a vast range of search terms to commence new campaigns and unearth long tail keywords, also check out your google webmaster tools
Simon