X22:  Stansted Airport to Colchester.

X30:  Stansted Airport to Southend on Sea via Chelmsford.

X5:   Cambridge, Drummer Street bus station to Oxford. see FAQ Page
http://www.stagecoachx5.com/faqs.aspx#9


In addition there is a two hourly service between Stansted Airport and Ipswich, which is an express service at just over an hour journey time.  This bus doesn't have a number, but is the Air Direct service run by Excel Coaches in conjunction with BAA.