I use newgroups and listserv's all the time.  They are great at answering questions.  A Word to the wise - you had better do your up-front work before asking everyone in the world to look at your little problem.  If not - you will be publicly flogged.  This has happened to me.  Most people will help you IF you do your homework.  Look at the makers website, look for previous questions/answers http://groups.google.com/ is great for this.  Tell what OS you are using (NT, XP, 2000, 2003 etc).

Don't post with a subject of PLEASE HELP NOW, this will make everyone ignore or reply with something *cough* less than helpful.  A subject of "Win XP Pro SP2 Error message 12345 can't print" and then a detailed list of what you did and what happened is much better.

Note - once you post to a public newsgroup, http://groups.google.com/ will come along and archive it FOREVER and FOREVER for ALL to see.  FOREVER.  Use your spell check and do your research.

With that said, here are some newsgroups that have proven useful to me:

Sunbelt Software http://sunbelt-software.com/community.cfm  Some groups are high traffic.  Exchange list is very high traffic!  NTSYSADMIN is helpful.

Veritas Backup Exec http://news.support.veritas.com/

Vamsoft Open Relay Filter Corporate Spam Filter - news.vamsoft.com (use an NNTP reader)

Servers Alive http://www.woodstone.nu/salive/mailinglist.asp

Micro$oft  msnews.microsoft.com (NNTP) This is difficult to use due to the large traffic.  But some Microsoft MVP's may answer your question.

Novell  CNE net http://cnenet.novell.com/  Novell Certified only access

Sonicwall Yahoo group http://groups.yahoo.com/group/sonicwall/- Sonicwall (Have not used since 2003)

Security - for home users only http://grc.com/default.htm.  I use these newsgroups sparingly - Lots of 'noise' here.  There are some very good nuggets though.  I can take Steve Gibson in small doses.