I used ImageMagick a set of command line tools to do image manipulations. For me it is the easiest way at the moment, but when you are not familiar with the command line or batch scripts, than you should probably look for some other method.
If you want to know I did something like (I don't have the code here so perhaps I made some mistakes):
convert image.jpg -bordercolor white -border 25 -gravity SouthWest -font Arial -pointsize 20 -draw 'text 25,25 "(c) 2011 David Perfors"' output.jpg
Thanks Donald, yeah I really think that you can learn a lot of looking critical to your own images. Criticizing your own images and images from someone else, AND letting others criticize your own images is something everybody should do... (Now I only should criticize others images...)