I just moved to the area and looked at ALOT of places!!! (40+) I had to also go up in rental price because we could not find a place to live. Craigs list is an okay site but I also used
jenalpollard.com
I am trying to remember the other 2 that were helpful because they list a map and did pinpoints of the houses so that you could see where they are located. Herndon has some nicer homes but is further out. McLean is a nice area that is not far from the city. Since you are younger I would consider a townhouse or an apartment. (rentals.com was the one that helped out)
Good Luck to you.