I have a MBP that I like to connect to my widescreen monitor when i'm at home, but I also use it at school and on the road every day. I like spaces because it gives me more space, but is there any way that you can just have 16 spaces, and view one on both screens rather than have 16 odd-shaped spaces that cover 2 screens?

That way you still have the advantage of dual monitor, you still have the advantage of spaces, but when you disconnect the external monitor nothing changes and you can just view the same space on the laptop screen, but only one at a time instead of two.