A good friend is involved in this and asked me to help spread the word.

From the page on the Second City site:

For the fifth straight year, a group of current performers and alumni of The Second City take to the stage for an entire 24 hour period to benefit children and families in the Chicagoland area during the holiday season. Improvised scenes, songs and games are performed by the ensemble, only taking breaks when a variety of top musical acts drop by to perform and inspire the cast and audience.

As a special treat this year, Second City and Saturday Night Live alum Horatio Sanz will be flying in from New York to join the cast!

Scheduled musical acts for “The Second City That Never Sleeps: Letters to Santa” include Jeff Tweedy, Robbie Fulks, Shellac, Sally Timms, Jon Langford, The Blisters, Jason Molina and many more.

Go here for the schedule and times.