Left rack:
Top two servers (with the blue LCDs) are new Dell boxes, they run ESXi and a bunch of VM's (we're migrating most of our core services to VMs)
The 4 boxes below those are IBM eServers that run services. Two of them are Kerberos KDC's (master and slave), one is DHCP and other essential services, and one used to run services that have since been migrated to ESXi.
Below that is a Dell server that runs Windows Server 2.8k. We don't host our own AD but it does serve group policies and such to our machines (we're a small portion of a much larger network).
The three yellow boxes beneath those are Google GSA's and run Xen VMs. We're working to migrate these all to ESXi but some of these services require an entire system outage to migrate.
The 4 boxes blow that (some of which are disk arrays) are for the AFS file system. We have 8 servers running AFS, several of which are virtual.
Right rack:
Monitor and KVM, self explanatory.
The top non-rack mount Dell server is an AFS box.
Below that is a netapp which started beeping and we eventually unplugged, because we don't really use it or know what it does.
Below that is an IBM B40 that runs backups. Nobody really knows how it works, or even if it's working at all.
And finally, the eServers below that used to do things, but were migrated to ESXi and now do nothing.