Not as many as I thought, but enough decent ones for a Top 10:
Yellow Magic Orchestra
La Monte Young
YMO would probably have to be tops: some fine albums in their first incarnation (1978-83), a great reunion album in 1993, and they're still performing (Live in London 2008). All three have had interesting solo careers - particularly Sakamoto and Hosono, but Takahashi has had his moments too - and I feel privileged to have met each of them when we lived in Tokyo. But I suppose I'd have to say that as a group they never quite made a classic.
Yes might be an unfashionable choice, but I was a big fan in the early to mid 70s, thanks to my big brother, and particularly of Yessongs. It had it all: triple live, side-long tracks, ridiculous lyrics, expert musicianship, a drum solo, and of course a multi-gatefold Roger Dean cover. Neil Young (also passed on by my brother) was another 70s favourite, especially After the Goldrush. But I lost interest after about American Stars and Bars.
Yello's quirky early releases as a trio up until You Gotta Say Yes to Another Excess were great, and even the post-Peron duo of Meier & Blank made a couple of late 80s corkers. However, for me Meier's most creative moment was in 1972 when he installed a plaque in Kassel railway station which said "On 23 March 1994, from 3 to 4 pm, Dieter Meier will stand on this plaque". And he did. More synthpop: I'm a bit of a sucker for Yazoo's two early 80s albums (and like many bands from that era I gather they've reformed).
More from Japan... Stomu Yamash'ta: lots of albums as Red Buddha, with the Go project and as himself; wacky Akiko Yano, ex-wife of Sakamoto and great artist in her own right too; and Susumu Yokota who continues to release an (ambient/electronica) album or two a year. Youth (aka Martin Glover) gets in as producer, DJ, Killing Joke founder, strange albums with Paul McCartney (as The Firemen), an even stranger album with Ben Watkins in 1984, and occasional solo artist. To be honest, La Monte Young is included more because I like the idea of what he does (very very long minimal drones) than for what I've actually heard (not much).
And the rest... Gabriel Yared (French soundtrack composer), Yo La Tengo, The Young Gods, Yeah Yeah Yeahs, The Yachts (whom I saw once), Yellowman and Yin Yang (one half of German synth duo Tyndall).