Here are a few more tools:
http://web-sniffer.net/ - Best search engine simulator tool I've seen (useful for peeking at cloaked pages
)
http://www.webhosting.info/ - Not only a domain WHOIS, but also a reverse IP tool (looks for websites hosted on the same IP).
Although the Overture tool is good, here's a better one:
http://www.123promotion.co.uk/ppc/index.php