SpyFu is online keyword research tool that is currently free, that will probably go paid. It allows you to spy on your online competitors keywords and Adwords to find the best ways to compete or spend your time and money try to advertise elsewhere.

More keywords! Knowing what the Top Paying Keywords can dramatically improve your earnings from the Google AdSense Program. Read on how to improve bad AdSense Ads, get info AdSense click fraud, and how to improve your profit on high paying keywords.

[tags]google+adsense, seo, sem, keywords[/tags]

A nifty idea by Great Paying Keywords allows you to quickly search through an A-Z listing of Free Google Keywords allowing you to compare the max and average costs of thousands of mainstream keywords. The website states the dollar amounts are calculated over the past 180 days. Tons of keywords and a great guide for anyone who buys keywords.
[tags]Google, Adsense, Search Engines, AdWords[/tags]

Using the Google Datacenter Watch Tool will allow you view your rankings for keywords across the different Google Datacenters at the same time.

[tags]google,search,internet[/tags]