Where to start C-programming open source?

Hi C-programming list

It's awfully quite here, I wonder if I'm even in the right place!?
I have been a programmer for many year, and dabbled in many different 
development areas, but I really want for participate in a open source 
project by developing C. I have looked over a number of mailing lists 
like Git, Samba, Vim etc. And every time I think "Wow, these guys are 
really smart, this is out of my league" - so how does one start?

Any comments and advice on getting started in OS with C is greatly 
appreciated.

- Carsten