You have to use an external monitor via Mini-DVI ($20). I was able to hook up my Dell 2007WFP (1680x1050) from my Macbook just fine. Other than that, you really shouldn't be going any resolution higher than the native.
If I remember right, there are no higher resolution 13.3" displays available. There were (if I remember right) 1440x900 12" displays that could fit the 12" PowerBooks though.
So no, you can't get any higher resolution on a MacBook.