Monica ESTJ, seen her referred to as an ESFJ as well which doesn't seem that far-fetched.
Rachel ISFP, the only one I've put as an introvert, but probably does have a lot of ESFP moments.
Phoebe ENFP, She's too much in a fantasy world to seem a J or an S, she's possibly an introvert though.
Ross ENTJ, I hate him, I hate him, I hate him, and want him as far away from being an INTP as an NT can get.
Chandler ENTP, arrogant like an INTP, but too obnoxious, has to be heard too much. His jokes don't change either like an introvert may try to do.
Joey ESFP, see the "ESFP" stupid myth. Can't be bothered adding a link.