I have been using Fetch. Very reliable. I upload to 7 sites, the same stuff to each one. I used to do it serially. Then I found out that Fetch can handle multiple uploads at the same time so now I open 7 windows and then drag and drop to each.
What would be better is to select 7 sites and have the software load them automatically to all of them.
I know there are some microstock programs that do this but some charge and others seem to not service some of the sites.... but I could be wrong.
Any ideas..... and and its got to work on a MAC