I wanted to order photo prints from an online shop. The problem is that those shops upload tools are not very effective under Linux. Although they propose native tools under Windows and sometimes Mac, the solution for Linux users is a simple HTML form. When you have to upload 100+ photos, it's not very convenient..... Sometimes you get a useless, buggy, Java applet.
The best solution I've found is to use Picasa for Linux. After you import your pics in Picasa, you click order prints, choose your prefered shop, and your photos are automatically transfered. You then just have to confirm your order and you're done!
Although running on Wine, and as such not a native application, Picasa for Linux is quite good. It won't replace Digikam for me, but it's a good complement. A negative thing is that when you import pictures, it copies it under its own directory ~/.picasa, which can become a waste of storage space.
Although my prefered option would be to use a Firefox extension to upload photos to the print shop, like Yahoo Photos had, this Picasa will do well enough.