If you don't have much time to play chess, a good way is to use Time For Chess. It's a kind of correspondence chess that you use with a browser to play, instead of mail or email. All your games are stored there, and you can make a move whenever you have the time. You can play up to six games at the same time without having to pay anything.
Depending on a game's settings, you can take days to make a move. This makes it easy to play people from around the world without having time zone issues.
To use this, you don't have to download anything. Just go there and sign up and play!