Well Hauppage sells a cheap PCI ImpactVCB capture card with 3 inputs but I guess you can only use one of them at a time!
If you are looking for multiple simultaneous capturing you are most likely going to have to get an older Viewcast Osprey card like the Osprey 230 with the dual beakout panel. You can capture multiple streams with their SimulStream software I believe.
Never used it myself, however!