Boot from a rescue CD (Ubuntu live CD, sysresccd.org or such). If your /var is on a raid set, I'd try to investigate with the appropiate raid tools before trying an fsck. If it's a simple hard disk, I would try
fsck -y -f -v /dev/partition
the -f means force a proper check, the -y means to do whatever fsck proposes, the -v means verbose.
But don't blame me if you lose data - if it's important data, best bring the disk to a specialized company.