I have CCM 5.1 running on an HP Proliant DL380 G# with no issues. The minimum requirements are DVD drive, 2 Gig memory and 72Gig HD's. No special tricks or hacks. For DLU's I first built a CCM 4.1 system with 10-12 phones then did the upgrade procedure to get to CCM 5.1. Otherwise you have to purchase DLU's from Cisco, $$$$$$.
I have heard of some people running CCM 5.X on VMWare on other hardware but haven't done so myself.