I have some Anubias attached to a cave-like rock. My betta likes to swim around in it or sometimes hide in it if I happen to have my hands in the tank.
my female tank (formaly Poseidon's tank ) has hygrophila, anubia nana, java fern and java moss. Java moss is really nice for betta, especially is you have alot of it. They can swim through it, around it and rest in or on it, very versitile.