HP have recently updated their Proliant Microserver to sport a slightly nippier processor. As well as the 250Gb SATA drive it also now comes with 2Gb RAM as standard – although if you're thinking of using one for a home lab Virtual Infrastructure you'd need to replace that with 2 x 4Gb sticks anyway.
HP's ongoing cashback deal for this little gem is still running too. Before cashback they're about £200 + VAT meaning that once you get your cheque back from HP, they work out at only £120 each. Not bad at all for a home lab and the AMD NEO N40L 1.5Ghz dual-core processor should be enough to handle a reasonable lab-like load.
ServersPlus are one of the places in the UK to pick one of these servers up. They even offer an ESXi 5 testbed bundle that includes the 8Gb RAM and an optical drive.
These little servers are great lab servers if you need something small and quiet. I have 3 of them running more or less full time at home and my wife hasn't complained about the electricity bill… yet.