The Turtle Island (String) Quartet
"Who Do We Think We Are?" (CD)

This recording has been on my shelf for a long time. I seem to remember this was in the Columbia House "clearance" section at one point, and having been recently introduced to the TISQ (probably by MPR) I gave it a shot.
It's never disappointed, even today, 17 years after its release.
The TISQ was first on the scene in an age before Mark O'Connor/Edgar Meyer/Yo-Yo Ma/Chris Thile/Nickel Creek began to blur the lines between acoustic, bluegrass, folk, classical and jazz. In fact, before then, there was probably little aside from David Grisman and Stephan Grappelli.
I think this was still the first time that my staunchly-classical ears considered that you could both play "fun" music and sound good at the same time.