Hardware options for compact micro cluster?

I'm working on a deployment for which redundancy and uptime are more important than processing power (existing testbed runs just fine on a quad-core i5 with 8 gigs of RAM.) Is there anything out there which would allow a 3-4 machine cluster to be built in a single chassis with fencing hardware onboard? I'm imagining a physical configuration similar to a Supermicro 2U Twin2 or some other micro-blade chassis but I've not been keeping track of the hardware race for some time.

thanks~