On one of my sites I exchanged some links with other sites in my niche. At the time of the exchange, their PR was equal to mine and the page showed up in my links recognized by Google. However, I have noted that many are not showing up in Google now even though my resources pages are a PR3. Are these no value links dragging my site's SERP down? What do I do? Contact the webmaster to notify them that they are being deleted?
If their link page is cached by google, google knows about the page and the link still has value to you as far as SERPS are concerned. If your main concern is PR then it may be a negative net to you but has nothing to do with SERPS. I would keep the link exchange as long as their page is cached.
PR figures are terribly unreliable. If it's a quality site, there should be no harm in keeping the link. As Rebert said, definitely check google still has their link page indexed. I've know webmasters to remove all links to their links pages which does make them worthless. If that's the case, don't waste your time notifying them that you are removing their link.