I've already mentioned it in fb_clients, but I have a nice little simple client, KodeFoto. And now a nice new version.
Its still not complete, but i've been using it for the past month or so. you are able to create new galleries, upload pictures (including directories).
The only thing is it isn't that good about checking username / passwords.
I really like dragging a directory of images into the client, and uploading it to a gallery.
I do it alot with screenshots of certain games, or a days worth of photos. It'll create a sub gallery with that directory name and put all the photos in there.
It uses .NET, so you'll have to make sure you have the redistributable runtime libraries. I've been thinking about doing a re-write so thats not needed, but that won't be for a while.