Here is some zip code information: http://www.mris.com/reports/stats/route.cfm;
I also have a market snapshot feature on my web site (home page - the report is emailed back in minutes, but you'll need to provide your email to receive it) that is intended for sellers, but can be used by buyers, as well. If you do not already have an agent, I'd be happy to work with you, I often work in Herndon. The last home that was for sale in Middleton Farms @ just under $900K went under contract in only a few weeks, so it is priced right - you'll need to move quickly. Let me know if I can help.