Operating System Sucks-Rules-O-Meter - The web-based operating system quality and approval metric.
Internet Operating System Counter - Statistics on Internet OS use, WWW, FTP, and News servers. Over 940,000 hosts checked in this 1999 survey.
OSNews: Exploring the Future of Computing - Weblog style online magazine on operating systems and computing environments. Daily updates, reader forum with many comments.
Convergence International - The non-Wintel user group, supporting Acorn, Amiga, Apple, ARM, Be, NCs, PowerPC, Psion, Unix and other alternative operating systems. Services include a non-Wintel news summary.
Operating System - Growing article, with links to many related topics. Wikipedia.