Terra Firma, off the beltway in the heart of Pikesville, is the Baltimore-area's most comprehensive store for jewelry making supplies. They carry a lot of tools for metalworking and bead stringing (although not many beads) and stock a good supply of precious and semi-precious metals. Their book selection is decent. They even have tools and books about gem cutting.
The store is an old-fashioned kind of store where the proprietor knows where everything is but customers can't always find what they want--things are in piles and stuck all around the place. There's lots of variety but only one or two of each item so the particular item you want might be sold out when you're there. The manager is very nice and helpful.
The store itself is not easy to find. You have to weave through parking lots off of Reisterstown Road opposite Boston Market to get to the store. The entrance to the store is semi-concealed at the back of a building, but it's worth the trip if you want to make jewelry--Michael's doesn't sell stuff like this.