http://www.jmbsoft.com/software/ags/?ref=fusionx
JMBSoft has Autogallery, Autogallery Pro and Autogallery SQL.
Autogallery is free, so if you like that you can upgrade to one of the others.
I use AG SQL on two sites and it's pretty sweet. Auto-thumbnailing, import galleries - it does just about everything you'll need (or even want).
Comus is awesome - I didn't use it for two reasons; price is higher than AG, and, it's not as simple to set up and operate (in my opinion).
Good luck!