There are several opportunities for folks to help out. Developing and supporting a complex program like Media Gallery is a very time consuming task. Anything you can offer will be appreciated.
If you want to get involved in the development efforts, there are plenty of areas where I would appreciate help.
If you enjoy using Media Gallery and just want to say thank you, then post a note in the forums. If you are so inclined, donations are accepted. This is my hardware/software fund, so any amount is always appreciated, but never required!
If you have an idea where you want to get involved, just let me know.