You don't need seperate paper or other such nonsense. That is only for countries where having a stamp might be a problem (Israel, Cuba, etc). You will be surprised how long you can go with a "full" passport before somebody will say something. They will hunt and hunt and use up every available spot. I have even had them overstamp other stamps. Even the Russians will look for any empty place to put their stamp.

Americans can add 24 pages, twice, to their passport and it is usually a same day service at most embassies as well as being free.