Wow there are so many to list. Here are just some that I've found (I also found this site with ALOT of species in real life too):
Pulchra
Samragdina
Macrostoma
Pugnax
Bellica
Schalleri
I'll get some more once I find the site. And the answer to your question is yes, they can cross breed with other betta species. The problem is that in the past, there were few wild bettas and people crossed breed wild bettas and betta splendens so much that wild bettas soon decline. It is advise not to cross breed bettas and keep the gene pool pure.