client
piece of software accessing a server service
thin client
lightweight computer optimized for connecting to a server
Tweetie
Twitter client
fat client
type of client over a network powerful enough to perform significant computation
news aggregator
client software that aggregates syndicated web content
email client
computer program used to access and manage a user's email
Google Talk
former instant messaging service
instant messaging client
software for sending or receiving chat messages
Gravity
Twitter and social networking client for Symbian smartphones