comp.arch is a wonderful Usenet newsgroup about computer architecture. There is a very good SNR for the newsgroup. Conversations involve discussions of ISA design, how to squeeze performance out of particular microprocessors, and the evolution of computer architecture from its origins in the 1940's to modern times.
The regulars of the newsgroup include hardware designers who developed some of the most famous microprocessors in use today such as the P6 core used by Pentium Pro and newer chips from Intel, and the MIPS processors used in Silicon Graphics workstations (as well as other things). One of the original designers of the UNIX operating system is a regular in the channel, as well. So there are definitely good pieces of advice flowing regularly through the conversations in this newsgroup.