i saw something interesting while shopping at JHittleSewing this morning. they sell packs of printable foundation paper that washes away when you're done.
it's a bit pricey, and the sheets are only letter-size, but for small foundation blocks i think it might come in pretty handy.
there are several pages of specials, so you may have to hunt for it once you go here:
http://jhittlesewing.funoverload.com...ls/page_1.html