The Best Cities & States to Find High End Gear

+1 jmcgrogan. Craigslist is a crapshoot that might just put you in touch with someone suffering from Methadone withdrawl.
Hifi Shark list almost all listings.(It can miss a few).
Bob

Ebay is great for buying beat up junk.Good luck.

I wouldn't trash Ebay altogether. 
I sell a lot on Ebay, and my equipment is hardly 'beat up'.
Due diligence is required, and for the most part, Paypal and Ebay are on the buyer's side. 

I agree with all of the above websites; never been on HiFi Shark and will check that out.  You would be surprised of the bargains that can be had on CL though because people just want to get rid of stuff there.  Several years ago I bought a pair of Paisley Research AE500's for $75.  They are super rare, incredible cabinets and sonically on par with ProAc Response 2's and Celestion SL700's, IMHO; by far the best sounding speakers I ever owned.  I recently sold them for almost 5X more because were just too big for my new listening environment. 

Craigslist is high risk, high reward. Yes, you may find a screaming good deal with some woman selling her husband's gear cheap when she's pissed at him. You may also find a criminal looking to rob you.

For those who like to live dangerously. ;^)