I've recently gotten into indoor rowing. It is hard but so much fun!
In addition to my awesome work out schedule I am also going to do the Concept 2 Holiday Challenge. The challenge consists of rowing 100,000 or 200,000 meters between Thanksgiving and Christmas Eve. Not only does this keep off the "holiday weight" but, according to the Concept 2 website, "For every person who rows ... at least 100K during the challenge, Concept 2 will donate $.02 for every kilometer (1000 meters) you accumulate" to a charity. I think that's pretty sweet.
I've calculated it out and I can row (on average) 5,700 meters in 30 minutes. So it'll take me about 9 hours to row 100,000 meters and 18 hours to row 200,000 meters.
18 hours of rowing in 30 days.