Check this out from the danish vmware user group:
It's written in perl and you need to modify some lines inside the code.
I haven't tried it by myself (but I will look at it soon).
I have found that snapshots do get in to a mess sometimes, and that VC does not always hold the correct info in these cases - so I quite like the snap_hunter script by Mittel from Xtravirt. That bases its info on an "ls" of the vmfs volumes on one of the ESX servers in the datacenter:
If you like that - I have added a bit more functionality to it - but am waiting for Alex to review it and publish it (if he likes it). If you give me your email address (or PM me with it) - I can send you a copy of the amended version.