Ideally, I'd like to run various video inputs (HDMI, compondent, etc.) into my receiver, and run one single video output (HDMI) to the plasma.
Is there a way that a receiver can force multiple video input sourcing (HDMI, compondent) to a single video output? If so, what is this called and so I can purchase the proper receiver?
It depends on what other components you will hook up. If you will be using any devices that output in an analog video signal you need a receiver that has an analog to digital converter. Also, if you want the receiver to be upconverting those analog sources to a HD resolution you will need an upconversion chip as well. You will best off going to a educational website like cnet.com or going to a local retailer to get answers to your questions and ideas on what kinds of products do what you want as well as prices. Most if not all high end receivers have those features.
I believe there are AV receivers which can take any video input and output all video via HDMI. At least that's my understanding of the Onkyo TX-SR875 for example. I expect the bigger Denons, Pioneers and Yamahas will do the same.
Some AV receivers will also have the capability to upscale the video output at the same time. This may be a useful feature if the scaler in your display isn't up to much, but if it's a good display you may not need the feature.