Minimum required as of today for HR is 331 (exclusive of deleted entities), as Jonathan said. Deleted entities are
counted in the mixed DXCC listings: http://www.arrl.org/system/dxcc/view/DXCC-MIXED-20121105-USLetter.pdf
Note that the top total on the mixed listing is 398 entities, and that there is one station with 386 entities who is not on the HR.
The honor roll listing is found at: http://www.arrl.org/system/dxcc/view/DXCC-HR-20121105-USLetter.pdf
The thing I find striking about this listing is that roughly one third of the stations on the mixed honor roll are at the very top, with all 340 entities confirmed.