The funny thing is that the most part is for dealing with LVM. If you have a “normal” encrypted partition, then mounting it from a LiveCD amounts to this (first do ‘sudo bash’ to get a root shell):
# aptitude install cryptsetup
# modprob dm-crypt
# cryptsetup luksOpen /dev/sda2 mount_point_name
Enter LUKS passphrase:
key slot 0 unlocked.
Above, ‘mount_point_name’ can be any name, it does not have to be a directory.