Cave Story is an incredible game. I'm pretty happy it's becoming more popular now (the 3DS version, the Wii-ware remake) so more people can experience it.

I know around '07 there was a pretty large modding community making some real nice mods. I'm pretty sure it must be around still.

Also, Pixel (the creator of Cave Story) even made this program that lets you compose songs. It's a kind of tracker, but it's real good for some types of video game music, it's called PxTone.