www.net-model.com

and there are others out there as well - but i cant remember where i found the links... google "online model portoflio" or some variation thereof...

As for payment some models are ok with doing it as a collaboration of services - they are a model wanting to get a portfolio up and you are a photographer wanting to do the same - so if you find a "begginner" model then you have a perfect match-up, because obviously those with portfolios will want some payment.  Put up an ad at a local college or uni and present it professionally and you will get professionality in return hopefully. (by that i mean say exactly what you need and be honest about it from the start - ie are you going for nude, semi-nude, fashion, fetish, or whatever?)

I am in contact with a model where i am and we are doing a similar thing to what i said above.  A group of us is organising a studio session and we get to throw her around a studio in various poses and she gets the pics out of it :)

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
Man is the dream of the Dolphin"

Rich Meadows Photography