I've posted this on other threads on this forum, but here it is again - this guy lives in PW County, and has a scanner streaming that scans PW County, VSP, and Fairfax County
http://www.angelfire.com/extreme3/alamoanasundayride/scanner.html
As far as a good scanner for picking up Fairfax County, you will need a digital trunking scanner (as has been said here before). Expect to shell out some cash though. You're lucky if you can get one for much less than $500.
I have a Uniden BCD396T - Great scanner - I highly reccomend it