We're reinstalling domain controllers in 50 primary schools, at the moment they are all standalone domains. We're joining them all onto a single County AD, the primary servers will all become RODCs then.
I frequently run VMWare ESXi on an Optiplex 780 which I take about with me, it has a pair of SATA 1tb discs in it and 8gb of RAM. Its usefull for P2V'ing an existing server onto and the reinstalling the hardware without any major outages. One thing to look out for is VT support on the CPU on your VM host, I originally had an Optiplex 760 but the Dual Core CPU in it didn't have VT, so I couldn't run any 64bit VMs (so no 2008r2).
We've been deploying Dell T310 servers to primaries recently, running vanilla 2008, Quad Core, 4gb RAM, 3 x 1tb SAS in RAID5 plus LTO drive. These come in at about £1800, been thinking about trying an Optiplex 780 with a RAID1 card and a pair of 1tbs instead for primaries, we'd be able to replace them quicky if anything failed and would cost £600. Anyone do anything similar?