Mac Friendly Online Group Photo Management?

I'm photo editor for a small publication, I have 3 staff photographers and 2 freelancers and I'm looking for an easy to use online service (PHP, CGI, SOME WEBSITE Whatever...) thats easy to use for my photographers to upload their photos to. I thought why not use flickr but the proves problamatic as it would cost too much to buy each of my photographers Pro accounts, I need something that I can run off my own web server and where I can organize all the photos by photographer. This way they don't have to make their way to my office and bring me so many darn cd's. It needs to be both Mac and Windows friendly. AND DON'T SAY GALLERY BY MENALTO. I already know of that solution and uploading photos to that thing is a bitch.