There are tons of options in the area.
For instructional courses, and if near the Inner Harbor, the easiest option is probably the Downtown Sailing Center in Baltimore (DSC). They have various programs at different levels from dinghy sailing to J24's, racing, cruising boats etc. I know several people that started sailing/racing there and have always spoken highly of it.
I second the Downtown Sailing Center, some really great people there.
For the sake of completeness, there is also Getaway sailing, a commercial outfit that offers classes. I believe you can also rent their boats.