Locust Music reissued a 1970 LP of a group that did modernist compositions for Gamelan Ensemble that looks pretty interesting.
There is also a local group here in Minneapolis that does the same type of thing. They are called the International Novelty Gamelan.
http://myspace.com/internationalnoveltygamelan
Nonesuch put out a few good Gamelan LPs in the 1970s as well.
I also have a bamboo gamelan CD that's pretty good. It's called "Jegog: The Bamboo Gamelan Of Bali," performed by Werdi Sentana.