I've written much here about the Los Angeles-based improv troupe The Black Version and gone to see them many a time. Here's a piece about them and about the state of improv in L.A., especially involving actors of color.
The Black Version is performing tonight at the Brava Theater in San Francisco as part of the SF Sketchfest series. Then they're performing Monday, January 29 at the Groundlings Theater in L.A. and on Saturday, April 14 at the Largo at the Coronet, also in my fair city. I have seen acres of improvisational comedy in my life and it doesn't get any better than these folks.