I'm surprised (or maybe I haven't looked hard enough) that this excellent site doesn't link you to the best ever Paris metro map. It's interactive, so you click on a "start" station and another "end" station and it shows you the best route and tells you how long it's going to take you to get there. AND, it's updated constantly, showing you where construction is going on, what stations are closed and how long, etc.

Wonderful tool: