Don't know of any sites but we have the evidence of hybrid cultures if not genetic hybrids. eg. Chatelperronian, Uluzzian and Szeletian. Should find something about them easily enough. How would the culture hybridize without at least social contact. Also the Portuguese skeleton that many people regard as a hybrid.

We also have modern evidence of hybrids between different-looking people. At least we do in New Zealand, perhaps less so in other countries. We always look at the world through the prism of our own upbringing.

There are many examples of hybrids between different species. Try following evolution of dabbling ducks online. There is nothing impossible about Neranderthal genes being with us still. If I come across any sites I'll let you know.