This is the prime source of foil data, from which all others seem to quote:
www.ae.illinois.edu/m-selig
but from sources such as this, you can get a foil drawn out for you:
http://www.windandwet.com/windturbine/airfoil_plotter/index.php
and here you can get .dxf files, which you need to be able to design a rig:
http://isoar.ca/~andrewm/rc/airfoils/19.html
If you haven't already got 2D CAD, I recommend QCAD from www.ribbonsoft.com - a very good package for very little money. I couldn't design wingsails without it.
These people seem to favour UI1720, a good foil for double-skinned hanggliders and microlights, which I would use, if I could figure out a way to make a soft wingsail with it, but I can't:
http://groups.yahoo.com/group/Airchairgroup/message/9522?threaded=1&p=9
and E1210 is also mentioned. That is a "General Aviation Foil" intended, I think, for low speed aircraft, operating in a very similar Re regime to a fast proa.
I stick with my Wortmann fx77w153 foil as being the most suitable for a soft wing.
Gardner has been discussing my soft wingsails with me elsewhere, and I am coming to the conclusion that a soft leading edge is not the way to go, for a fast craft operating with the apparent wind very far forward. It's right for me, with a heavy monohull, but not for a proa. I think that high speed sailing demands a hard, smooth start to the section, at least for the first 10%, ie a wing mast. I'm going to put a sketch of what I would do for a proa, based on E1210, in a folder in the files section, under my name.
David.