I would say the best way to develop communication skills for a shy person is to find him/her a great friend, who is always there for them. Now, this doesn't cure his/her shyness per se - but its a great start in the path towards building up his/her confidence. Confidence is the key for the shy person. Shy people are always short of confidence, they don't think they are good enough, they withdraw for fear of being rejected or not being accepted in a group. So, what better way than to find him/her that great friend, having whom would boost their confidence.

This friend can then introduce him/her to a wider group - gradually. Fact is that shy people don't make friends because they don't initiate friendships. Its not that they don't want to initiate friendships - they just can't or don't know how to! So, having a friend who can introduce other people to them is a great boon for them. As they gain in confidence, you'd find their hidden personality bloom. They'd show communication skills you'd never knew existed. Of course, they'd never totally become extroverts, but they'd improve vastly from their isolative introvert selves.