There are numerous histories of Maryland and the early families that lived there. I also remember seeing some good websites relating to Maryland genealogy. Try finding the websites through Google, and try Google Books for your family and histories of early Maryland. Try a regular Google search for a few of your ancestors, too, if you haven't already ("john doe"). It is also quite possible that your family landed in another state, and moved to Maryland. A great many Ulster-Scots landed in Philadelphia, and then went to wherever the pickings looked good. If you find an ancestor's name on an early census in another state, then you can look for more detailed records in that state.

Good luck.