Well this is one of my favorite games, and is fun to play, unless I lose! This game is quite popular in Greece so it is easy to find interesting opponents, however when searching for a good software backgammon game, there was none that good as the real one! By searching in the internet I've found the following games:
The last one is one of my favorites, but I'm dissapointed with all of these implementations
since the play only one game. That game is 'Portes' (foreign people call this 'Backgammon'),
which is the most boring of the tavli games!!!
For those who don't know, there are two other games for the backgammon board, called 'Plakoto' and 'Fevga', which are far more interesting than the backgammon game. View this posting for the rules of these two games. (although they seem somewhat stricter than normal game rules).