Wikipedia is the proof that a free system based on sharing can work and not only does it work, but it works better than the commercial equivalent (at least in my opinion). I don’t think a day goes by that I don’t end up looking something up using this amazing resource.
So, go ahead, support Wikipedia! Do it in whatever way you can, whether financially or by submitting content!*
* I am planning on starting a big Wikipedia-based project in the not too distant future to expand some sections that I care about and I feel are insufficiently developed. If you think you would be interested in helping out, let me know and I’ll give you more details.