For Keyword Research my favorites include:
Word Tracker – They offer a Free Keyword Research Tool and a Free Trial to their Paid Keyword Research Tool
Keyword Discovery – Free Trial for Keyword Research and Search Suggestion Tool
SPYFu – Especially helpful for keyword competitive research – SpyFu Combat lets you see what keywords your competitors are paying for – limited access without a paid subscription.
KeywordSpy – Helps you track keyword ranking and spy on the Pay Per Click ads of your competition
