VMware ESX 3 snapshots
Here's a CentOS 4 VM with 4 snapshots, in each snapshot I added a 40M file and in two of the snapshots i snapped the memeory as well.
Note a memory snapshot file is ALWAYS created if it doesn't contain anything !
The .VMSD contains a snapshot definition !

-rw-------   1 root    root        8.0G Nov 26 17:26 cent4-flat.vmdk -rw-------   1 root    root         334 Nov 21 12:39 cent4.vmdk
-rw-------   1 root    root        1.4K Nov 26 17:31 cent4.vmsd
-rw-------   1 root    root         48M Nov 26 17:28 cent4-000001-delta.vmdk -rw-------   1 root    root         219 Nov 26 17:27 cent4-000001.vmdk -rw-------   1 root    root         18K Nov 26 17:27 cent4-Snapshot1.vmsn
-rw-------   1 root    root         48M Nov 26 17:29 cent4-000002-delta.vmdk -rw-------   1 root    root         226 Nov 26 17:28 cent4-000002.vmdk -rw-------   1 root    root        257M Nov 26 17:28 cent4-Snapshot2.vmsn
-rw-------   1 root    root         48M Nov 26 17:31 cent4-000003-delta.vmdk -rw-------   1 root    root         226 Nov 26 17:29 cent4-000003.vmdk -rw-------   1 root    root        257M Nov 26 17:29 cent4-Snapshot3.vmsn
-rw-------   1 root    root         16M Nov 26 17:31 cent4-000004-delta.vmdk -rw-------   1 root    root         226 Nov 26 17:31 cent4-000004.vmdk -rw-------   1 root    root         18K Nov 26 17:31 cent4-Snapshot4.vmsn