How about putting the commands into a Makefile and running it with make -j 4? Easy! For a more heavyweight alternative, there are lots of solutions around for

How about putting the commands into a Makefile and running it with make -j 4? Easy! For a more heavyweight alternative, there are lots of solutions around for running batches of commands across multiple machines. For most/all of these, multiple commands on a single machine are just one of the simpler cases they can handle. Systems that spring to mind are GridEngine (http://gridengine.sunsource.net http://gridengine.sunsource.net), Qube (http://www.pipelinefx.com http://www.pipelinefx.com) and Condor (http://www.cs.wisc.edu/condor http://www.cs.wisc.edu/condor). There are plenty of others too (including a lot of home-brewed brewed systems knocking around inside VFX houses).