ImageMagick is a really cool (powerful) tool, once you get the hang of it..

With watermarks, you can set opacity, location, etc.. of the watermark.. which can be another image, or generated by the program as text (e.g. domain name in black using verdana)

From the command line, you can churn through complete directories..
Resize the pictures based on dimensions- e.g. max size 750px while keeping proportions correct
generate the thumbnail - 80x120 or whatever
watermark the original with another image at a certain opacity
place a border around the entire shot
alter the quality (if jpg)...

Did I mention ... It's free..
http://www.imagemagick.org/script/index.php