There's been many lists circulated, but as they age their dead-link ratio seems to increase on a curve.

 

Here's the current guide list that is actually from a semi-official source this time.  Lot's of cool stuff on here that I had no idea about, although it's too bad they've "rolled-up" some stuff (for example, all the MS Research downloads just get one link to the main MSR page... wouldn't even know about cool stuff like Pex and AutoCollage if you don't go visit the site).