What language?
What skills are you looking for?

A shell is basically a piece of software that is used as an interface for human beings to input text commands to other applications resident on a computer (including parts of the OS core itself).

http://en.wikipedia.org/wiki/Shell_(computing)

No journaling right? Wouldnt file system type selection also be important?

I like GNOME myself, not because its the fastest desktop environment but because its solid and never lets me down. I have noticed that when software just works it helps me suppress my incessant need to tinker and so im ultimately more productive because of this.

You could always browse through http://sourceforge.net/ and find a few projects you like the sound of and then follow their progress. After some investigation you could make a judgment call on which ones you think deserve your donation.

Of course there are other ways to contribute. For instance software developers find it very helpful when users log bug descriptions for their software.