There is a mod for gta sa where you can play online with others. It is very popular, and free. All you need is a copy of gta sa on your computer and download the mod from mtavc.com and hit download on the screen and you can get playing. There are many popular servers on it but I recommend CIT or SAES but you could always start your own server. There are many different types of servers like racing or deathmatching or roleplaying. Hope you enjoy MTA!