http://wordpress.org/wordpress-2.2-RC2.tar.gz
md5: 1535c8dbab84dea7f0338cba5e58bf2e
http://wordpress.org/wordpress-2.2-RC2.zip
md5: 96d038eb76c3970fb32b707962f23df2
The full diff between RC1 and RC2 is here
RC2较之RC1重点在widgets(小工具)上的若干修正和对最新的PHP5.2.2的兼容:-)