This really depends on what kind of kayak you have.
For sea kayak, I would stay near DC or the chesapaeke areas.
For river kayak/white water> there are so many places around here.
there really is some great kayaking around here.
-Bull run stream, from gum springs road to rt 28 and beyond, it takes you through some amazing civil war sites.
-Shennandoah river- the whole thing...great place few good rapids lots of great camping
-north fork of the shennandoah- great kayaking. a couple rapids, great fishing
- the confluence of the potomac and the shennandoah has great rapids, lots of fun, but I would take someone who knows whats up.
-the trip from point of rocks to shennandoah is fun , and surpisingly fast for a wide river.
- Cub run stream near centreville - belive it or not in the spring it has class 5 rapids.
-goose creek stream/river , its real nice, fast water, few rapids, but it empties out in the potomac above the algonkian park.
I would stay away from the anacostia waterways, its fine until you fall in, the water smells like shit.
get a book called "Virginia white water guide" it has a old guy in a canoe on the front.
alot there is a great website from the USGS , that tells you the water levels in real time
http://waterdata.usgs.gov/nwis/rt