You likely have quite a few problems I should think, given it's possible any databases, websites, mail spools and log directories have also died in there.
I would seriously recommend taking a block level backup of the disk before you start mucking around in it if you had any sort of important data on that server. dd if=/dev/XXX of=/somewhere/else/disk.img (from memory!)
While knweiss' answer will rebuild your rpm directory and program specific dirs and may let you continue using the server you will need to get in to the file system internals to try recover anything meaningful.
I'd also be concerned about any other directories that have gone missing that you haven't noticed yet. (...and I'm going to assume it really is a file and not just an empty directory where var is on a separate partition that failed to mount.)