I thought it would be useful to add this capability to nautilus, so I wrote something very quick and dirty to do so. I don't claim it's polished work: I wrote it in a couple of hours. Patches are nevertheless welcome. I'm also considering turning it into a libsharing plugin for the N900.
At present it doesn't allow you to delete the images you upload. I know how I want to do this, and you can probably tell from reading the code, but I left it out of this version for simplicity.
I think if this was polished up a bit it would be useful enough to package. What do you think?