KVM Solutions with Multi-head Outputs
Using a Synch cable between two or more switches will allow you to create your own dual or multi-head KVM solution, effectively switching 2+ displays between several systems.
Scenarios:

2 x PS/2 and VGA Switches to provide dual-head VGA |

2 x USB and VGA Switches to provide dual-head VGA |

2 x USB and DVI Switches to provide dual-head DVI |