I'm looking to get into Japanese teas

I've been a pretty avid tea drinker for a while now. The world of tea is huge, yet I feel like I've still barely scratched the surface. I've worked at a couple of teahouses that serve predominately taiwanese and chinese teas. Think tieguanyin, longjing, duck shit, jin jun mei, da hong pao, taiwanese milk tea, etc.

I've had some good japanese teas (gyokuro, sencha, genmaicha, high grade matchas, etc), but the teas I listed are about the only ones I know.

Do you guys have any recommendations as to where I might be able to buy some high grade japanese teas, and what types of tea I should try to expand my repertoire a bit?

I'm specifically looking for good websites, though any shop recommendations in the Pacific Northwest are welcome too!