Teshka - 7:20 am on Jun 30, 2004 (gmt 0)

I did the same thing several months ago when I noticed directory sites ranking inexplicably well. I added links to relevant high PR pages with my keywords in the anchor text and also saw a boost in the SERPs.

By the way, if you want to try this, you don't necessarily have to directly link to your competitors. For example, two of the links I added were to my sections of the Yahoo and DMOZ directories. You could also link to information sites.