sort of nonexistent... but along the lines of abstract sound art, you have people like Michael Pisaro and Graham Lambkin making interesting music nowadays.. individually, as well as in collaborative scenarios. it's hard to think of a modern group or band with the same impact or presence of sonic youth, what about autechre?
on another note,
jason lescalleet makes warped sounding music using tape machines, turntables, field recordings, etc.
discography is littered with gems, playing/recording scenarios where two or more disparate-sounding artists are put together, for interesting results. it's all loosely generalised as electro-acoustic improvisation