I'm always on the lookout for DC, MD, or VA gardener's web sites, blogs, etc. Here are two that Jim McKenney maintains does two sites: http://www.pvcnargs.org/, which is the local chapter of the Rock Garden Society, and his personal site, http://www.jimmckenney.com/. The latter, Jim says is" "My Virtual Maryland Garden, which will never be truly finished until I die; there is already lots of material there."
I love his personal site as an example for other local gardeners to not be afraid and jump right in with an online garden journal. Yours need not be picture perfect or close to completed, we lean just as much (if not more) from following those still in progress.
I notice that while we are a region rich in gardening wealth, our area seems to have a shortage of gardeners online and in forums -- as compared to those in Canada, UK, Northwest US, and Australia! If you know of a DC-area gardener with an online site, journal, blog, etc. please let us know.