It depends on exactly what you're looking for but
PhotoShelter is great. You can use it as an archive, for print sales, and for rights-managed licensing. A recent feature is the ability to use FotoQuote to set prices. You can also customize the look and feel as well as set up virtual stock agencies with other photographers. Very flexible and cool and they're nice people to work with. I'm with them and I also have a portfolio site through
liveBooks, which I also highly recommend. I'm in the process of having my PhotoShelter site integrated into liveBooks so that the archive, print sales, and licensing are combined with my main liveBooks portfolio site.
If you're just looking for hosting so you can roll your own rather than something specific for professional photographers, I can recommend
Pair. The various plans give you options like CGI scripting and mySQL databases. It's Unix-based, which I like.
Hope that helps!