Ray, I'm not aware of a website, but for the last 3 years, or so, the city dockmasters office has been in the same lobby as the Inner Harbor Marina.
Docking is on a first come basis, and there always seems to be room. After you tie up, the dockmaster usually shows up and writes you up. When you go to the office, they'll give you a pass card for the showers, which also works for the lounge for internet access. All of these facilties are Inner Harbor Marinas & the Citys. A real bargain.