As a multi-computer scenario, Condor might be interesting for you.

Condor lets you submit a program/batchfile/shellscript to a queue of many machines (nodes). Every one of these nodes needs to have a condor client installed. The condor client advertises the resources that that particular machine has on offer. This information is then used to match your job requirements to any number of machines. Advertised attributes are things like: CPU-type, OS-type, Amount of memory, free disk space, etc. If enough clients are available, your jobs will run simultaneously.

Condor can use dedicated machines, or take advantage of idle clients: running only on designated times (at night, for instance) or monitoring machine activity, and kicking in after some idle period.

Obviously, because clients need to be installed on all machines, it needs some organisation (=politics) to get authorization to run your programs on a sizable group of machines.