It would really be interesting to see a "computers-on-Jeopardy" competition that was open to all comers. (The 'Watson' appearance, while impressive in many ways, was essentially a contrived IBM infomercial.)
[1] http://trec.nist.gov/ [2] www.loebner.net/Prizef/loebner-prize.html
Jeopardy is a widely-understood game format; a competition-via-API would be understandable to a wide variety of competitors, from leading researchers to precocious cranks.
Outside TREC, there is the CLEF QA track[3]
[1] http://trec.nist.gov/data/qamain.html
The data they use is much purer, and makes a much better evaluation for general-purpose QA technologies.