Volume 2 of xxxHOLiC Rei will also be available in a limited edition format with the 2010/2011 OADs, xxxHOLiC Rou & Rou Adayume, on Blu-Ray. It will be on sale April 23rd. [more at the xxxHOLiC portal]
CLAMP has also drawn Saber for the 10th Anniversary of the Fate series. There is a lottery in the Type Moon Ace Vol 9 Magazine for the illustrated poster. [info at clamp-net]
ETA:
Amazon.jp has the limited edition Volume 2 up for preorder.
