From what I can see in the plugin section, there are two plugins for photo galleries which allow captions/descriptions:
WP Photo Album Plus
http://wordpress.org/extend/plugins/wp-photo-album-plus/
NextGEN Gallery
http://wordpress.org/extend/plugins/nextgen-gallery/
Are there any others that I've missed? I don't want anything too complicated, but I do have a need for descriptions/captions on photos. Some might be a paragraph long!
