Minimalism

I like some stuff like Ulver's Lyckantropen Themes and Silencing the Singing. Both of those albums are good minimalistic ambient as well as Vidna Obmana's "Spore" album. I also like some minimalistic black metal such as Burzum.
 
I've very much gotten into minimalist contemporary classical over the past year, my favorite being the works of Steve Reich.

Minimalism can pertain to many different genres, such as ambient, classical, and even some metal (Darkthrone's Transilvanian Hunger is a good example).