I've been waiting for someone to mention the talented performers of the mock-documentary movie A Mighty Wind
In particular, consider Jane Lynch, who's followed up the movie with additional musical work (see particularly a Christmas-themed project from a couple of years ago, including a lively version of "Up On The Housetop" and a very nice duet on an original Christmas song with none other than Dick Van Dyke). Lynch is best known, though, for her star turn on the TV series Glee.
Also worth mentioning from Wind is Annette O'Toole, who co-wrote wrote three of the film's songs and has occasionally done cabaret-style gigs with her husband, Michael McKean. Her acting credits run several screens' worth on Wikipedia; nowadays she is likely best remembered for her turn as Martha Kent, Superman's adoptive mother, on Smallville.