There are a variety of great tools that provide keyword usage and competitiveness data between both paid and organic search - some of which are really good.

Term Explorer - This is my new favorite tool. It does pretty much everything including pulling all search volume and AdWords data, making suggestions, checking recursive level, and even pinging the ICANN index to see if there's an EMD available :) Even better the bulk keyword research tool can handle up to 90,000 keywords at once and it will go fetch all of the data for you, and fast.

On top of the keyword tool, it has a keyword analyzer:

And a URL Analyzer that pulls page-level backlinks, domain backlinks, URL PageRank, domain PageRank, domain age, # of words on the page, and number of outbound links. Make sure you strip the "http://" from the URL's!

Keyword Snatcher - Excellent for initial idea and term gathering. You give it a head or body keyword, set a few simple filters, and let it run until stops. I've generated lists of over 30,000 keywords in as little as 4 hours.

SEMrush - Gives you fantastic insight into search volume, average cost per click, number of competing pages, related keywords, rank results, and even companies currently buying ad space .

SpyFu - Provides search volume, number of clicks per day and their average daily cost, the actual number of advertisers currently bidding on the keyword and the actual AdWord ads that are running.

Keyword Spy - Is one of my favorites for getting a quick sense of the landscape. It very quickly (through use of tabs) gives you access to data on PPC ads, related keyword phrases, your paid and organic competitors, and my favorite; misspellings!

Did you know that keyword reserach has an estimated 110,000 searches per month! See a screenshot of the dashboard below: