Here's another one for you to keep in your armoury.
NetDISCO is an oldie (well, there's actually a revamped new version available) but a
Although the purpose of NetDISCO is somewhat simplistic, it really is a tool you can't afford to be without in todays enterprise networks.
Essentially NetDISCO does exactly that (network discovery).
Once you add devices to it's database, it slurps their MAC and ARP tables and keeps a record of this over time.
Need to find where every device starting with a particular vendor ID component of the MAC address are connected throughout your environment?
Want to quickly see how many switches ACTUALLY have spare ports on them, and of the spare ports, when (if ever) was the last MAC address seen on that port?
You can grab a virtual appliance from over at http://wokka.org/netdisco/
As per the download site, once you've spun up the VM, config it as per:
Don't forget - the UI listens on port 5000!