I've been building a few albums on digikam
exporting to Picasa/Google+ works fine

a small issue is that the list of files to be exported should be cleared when I close the window,

when I select all the files in an album & click export, the export files from the last session are still on the list
I understand there is an empty list button
I suppose one could add individual files could be added to the export list, everybody's workflow is different.

I'm not positive there isn't a setting, but I can't find it
That being said, this may be a feature request