Fellow Warrior Andy Henry posted a large list of IM links and resources a few days ago, amongst them was this absolute gem:-

Download SEO SpyGlass 3.11.1, And Reveal Your Competitors Entire Linking Strategy

(Not an affiliate link)

What it does

It analyzes any url you type in and gives you an extremely detailed report on their backlinks, including the url, anchor text, page PR, domain PR. It's great for analyzing not only your own sites, but also those of your competitors. There's a paid version, but the free one gives you more information than Yahoo Site Explorer and Backlink Watch so it's well worth having. Enjoy!