Teresa, I have found that adding 1-2 tablespoons of molasses to the good old Tollhouse recipe makes the cookies moist and chewy, without changing the taste. I usually cut back the brown and/or granulated sugar by a couple of tablespoons to compensate for the molasses.

There has been much discussion at this board about the use of shortening vs. margarine and butter when trying for that perfect chocolate chip texture. You might want to do a search and find out what the great bakers here have to say. Good luck!