Try submitting them to an online gallery. That way, you can maintain control over the access levels via the site.

I love Corbis, great search functions and a really good company profile.

1. 1. Corbis: photography, rights, motion.copy

I use both bridge and photoshop to add in the meta data and file info my copyright information - I also add a layer with text on it using the © symbol which I then flatten and make it big and multi coloured but transparent so clients can see the image through it - see attached file. I also sell my work through agencies as stock they protect my copyright since they also act as my agent for the photos I have with them.

A real simple way is to add text using the windows stock "paint" package!

Start/All Programs/Accessories/Paint/Text(the A icon)/ then highlight the lower multi icon box in the same toolbar.

Not the prettiest, but Free!

As the taker of said photos you automatically own the copyright - your problem would therefore appear to be controlling their use - an online gallery would appear to be the best way - although I guess adding symbols and watermarks as described above will make it obvious and also perhaps more importantly stop people misusing your photos.