In 2013 I sang with the Dickens Carolers for the first time. A polished, professional organization, I thoroughly enjoyed the experience and hope to return in the future.
From 2005 to 2009 I sang with an a capella group of four to five people, all employees of Amazon.com. We sang mostly covers pulled from our various college groups libraries, adapted for the parts we had on hand; initially four men, then adding a soprano, then swapping in two new men when the soprano and original baritone left the company.
We just missed the ubiquity of smartphones before we broke up; as far as I know, no video of our performances survive.