I liked the idea of this photographer:
http://www.photoconnect.net/sell2a.htm
He is furtherly recommending alamy.com
maybe you find this article interesting too:
http://www.dphotojournal.com/sell-photos-online/

I further recommend Napoleon Hill: Think and Grow Rich (bestseller since
1937, you might find it as a free ebook here or there)

Now after lurking a little, I have a first question myself:

Is there an offeror (I'm actually sure there is a many, but which one is
really good in terms of quality and conditions) that uses a photobridge
through which an artist / photographer can sell his own pictures as
prints? What is required is a system where the prices can be set from
the offering photographer's site. In Europe there is f.ex. pixaco (but
doesn't allow customized prices) or bilderplanet.de which allows an
artist to define his own prices and they just charge the seller/the
artist their regular price as commission so to speak and he can keep the
difference.

As I'm not sure what you might understand under the term photobridge:
A shopping cart system which can be linked from the artist's gallery and
which allows the visitor of that gallery to order prints from a photolab
which gets the original print size models from the artit's websites and
gives the artist commission or control over price / transaction.
The photolab that is prospected for should ideally be willing to ship to
whole US, maybe Canada as well, take care of the whole order/payment
process and transfer the artist's earnings oversea or by electronic
means like paypal.

Any ideas what companies to check out?

Thanks a lot.

David