Here's the problem:
The "success" of such contests (and by success i mean the quality and quantity of submissions), is dependent on getting enough high quality people participating. For whatever reason, this is almost never easy for a small site like ours.
The reality of this world is that two sites can run identical contests and one site will get no participants and another will get 10000. And the difference will be based on the kind of publicity the sites get, the reputation of the sites, and the existence user base. For programming contests especially, much of the participation seems to be to be based on the accepted wisdom about the prestige of the site, rather than any details about the contest.
What this means is that for a site like ours, which doesn't specialize in linux, to hold a linux programming contest, is likely to get very little attention and participation.
So while it's a nice idea it's probably not something that we should spearhead. Truth is google can have a contest on how to build a nice looking simulated dog turd and they'd get 1000 carefully crafted submissions (and the contest would be features on slashdot.org and written up in the new york times -- and the winning dog turds would be installed as widgets on a million websites). We just don't have that kind of influence.
However, i think it would be nice to have a little mini contest or something just for fun, maybe building a cross-platform firefox extension or something. Something that has some cross-platform application and might be more narrowly tuned to the interests of users on this site. And not with big prizes, etc (which are a lot of work to organize), but just some cody mugs or something.