Well, for the mane there's always hunter braids and button braids, usually used in show. You can also do running braids for horses with long manes, and diamond braids. Google has lots of pictures to give you an idea of what they look like.
For the tail, you can french braid the top and leave the rest down, or you can do the same concept with an inverted braid, meaning you french braid upside down. Kinda hard to get the hang of. CloudMystique posted a cool tail braid a while back, too, where you divide the tail into three sections, braid each section as its own braid, and then braid those three together.