I imagine a lot of us on this site are fans of Mathematica's design principles (for both the language and function library). When a new version is released it is always exciting for me to see what new features have been polished enough to become part of the standard library. At the same time, I don't feel that software sophistication as a whole is improving as fast as it should (when compared to say the increase in size of datacenters). I think we are the right community to start building an open source, consistent set of extended packages for the standard library functions. We could contribute in a similar manner that we contribute here on SE (short bursts of work on a wide variety of problem domains), but this would also incorporate integration and organization work (building meta-algorithms, adding tests, etc). I had some initial discussions last week on the Wikidata mailing list, but there wasn't a critical mass of programmers that are used to working in short bursts on a wide variety of problems. I think that in exchange for our extra work compared to just answering SE questions, we would help build a resource that all of us would use to accelerate and expand our coding projects in ways that we haven't even imagined.
The Wikidata discussion is called "Accelerating software innovation with Wikidata and improved Wikicode": http://lists.wikimedia.org/pipermail/wikidata-l/2013-July/thread.html
I have a lot more I could say about this, including specifics on how to start, but I wanted to gather some more feedback after people have glanced at the Wikidata discussion.