So far we do know of 4 different mount types actually. Though as mentioned above more might be added. Horses of various qualities, trisons (a sort of buffalo), Ursaphant (appears to be more of a beast of burden), and a large otterbear capable of land and sea transport.
As far as weapons we do not have a list, but we do know some. Lance's and swords have been seen in gameplay. However I believe that this game will have a very large range of weaponry if you can find and learn the schematics to make them. I would say it is fair to expect all medieval weaponry to be in game. SBS has a picture of a mounted archer on a trison, so hopefully we can expect mounted range weapons from bows to javelins and throwing knives.