USENIX is great.  It publishes a good technical magazine called ;login: six times a year and puts on some awesome conferences including USENIX Security and LISA.  Membership is a little over $100 a year unless you're a student and gets you reduced admission to their conferences.  Check out their site: http://www.usenix.org .  Issues of ;login: that are more than a year old are free.  The December issue each year is dedicated to security.

I'd definitely look for those organizations that have a strong local chapter in your area.  If OWASP has a chapter in your area (and you have an interest in web) then definitely check them out.  Depending on your background, you could also check out Infragard (it always feels like I am misspelling that) to bolster some strong relationships with law enforcement.

I'm based in Mississippi, so not much in the way of local chapters around here, but I would definitely check these out if they were available.

Seth