Oooooooooh I think you guys are gonna like this! Nullbit has produced the SEOLinks Firefox Extension, an extension that allows you to hover over any link on a page and get linkage data from Google, Yahoo and MSN. It's slightly rough round the edges, for a time i thought it wasn't working, but it was like it needed to "warm up" heh.. as it works now, but overall, it's a very, very neat little app.
It'll also give you ranking dat across those engines for the anchor text / desination of the link you're hovering over. Very nice indeed.