Kind of on the Jazzy side of stuff -

Bela Fleck and the Flecktones, especially Little Worlds and Live at the Quick (here's his bass player Victor Wooten).

...which logically leads to 'jam band' extraordinaire The Dave Matthews Band, of which DMBLive Vol 1 is essential and features both Bela Fleck and Jeff Coffin of the Flecktones.

Garage rock rebirth band The White Stripes are of course fantastic, but should be known by everybody, suffering as they do from media over-exposure.

On the reggae front, theres the Hassidic reggae singer Matisyahu and yet more eclectic, there's The Dresden Dolls. If you don't know either, there's a surprise in store for you.

There's the commercially successful psych/space rock Mars Volta, the astonishing symphonic Glass Hammer and the more harmonic prog of Echolyn.

So there you go, modern American music that amuses me.

--
DrGoon