yankee:
Dunno about Collegeboard and how current their info is.
But, I do think that Cornell publishes accurate data, and that the link to its own Common Data Set in post #5 is correct: For the matriculating Frosh in fall of 2007, Cornell's 25th ACT % was 28 and its 75th % is 32. It is a statistical no-no to split the difference and end up with a mean of ~30, but it's not a bad estimate.
found Frosh of 2008 -- Uni-wide, the 25th increased to 29, and the 75th to 33. The endowed colleges (which includes CAS) are 30-33.
http://dpb.cornell.edu/documents/1000175.pdf