Summary:

Former Groupon CEO Andrew Mason and App.net’s Dalton Caldwell are joining Y Combinator as new part-time partners, in addition to each running their new companies.

Andrew Mason, CEO, Groupon

Famed Silicon Valley incubator Y Combinator announced Thursday that it’s added a new full-time partner and five part-time partners, and among those five are former Groupon CEO Andrew Mason and App.net’s Dalton Caldwell.

The incubator, which was extensively profiled by the New York Times Magazine recently, has emerged over the past few years as a powerful force in the early-stage startup scene in Silicon Valley. The group has both full-time and part-time partners who advise startups in the program, and Caldwell and Mason are both young, notable faces in the technology world.

Caldwell was the founder of the music-sharing service Imeem and now runs App.net, an open developer network for apps. I profiled Caldwell back in December, when he talked with me about his evolving attitudes toward the Valley ecosystem and the benefit of paid services.

Mason departed from Groupon about three months ago in a fairly memorable firing announcement that included jokes about Battletoads and fat camp. Mason wrote in a blog post that he would be launching a new company when he moves to San Francisco. “I’ve accumulated a backlog of ideas over the last several years, my favorite of which I’ll be turning into a new company this fall,” he wrote.

And in more entertaining news, Mason wrote that he will also be recording motivational business music in L.A. Hopefully he got a coupon for the recording studio fees. From Mason’s blog post:

 I came to realize that there was a real need to present business wisdom in a format that is more accessible to the younger generation. It was with this in mind that I spent a week in LA earlier this month recording Hardly Workin’, a seven song album of motivational business music targeted at people newly entering the workforce.  These songs will help young people understand some of the ideas that I’ve found to be a key part of becoming a productive and effective employee.  I’m really happy with the results and look forward to sharing them as soon as I figure out how to load music onto iTunes, hopefully in the next few weeks.

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