Aaron of SEO Book has updated his Link Harvester tool. It's a link analysis tool that uses the Yahoo API for conducting link research.

Donna from SEO Scoop offers a great description:

"It shows you unique domains linking to the site, including the IP address and unique C block addresses of the links. It also isolates links from .gov, .mil., .edu and .ac.uk domains as these links are likely to have greater impact. It includes links to archive.org, whois, and Google cache near each link. In addition, it allows importing to .csv (Excel) format. Put your competitor's url in the form and find out just how strong his backlinks really are, or use your own url and discover where your weakness lies."

I would definitely recommend checking this tool out as it makes link opportunity identification and competitive link research a snap.