There's a travel center just outside the customs area. The airport Web site is part of the BAA Web site with links to seven British airports. BAA is the British Airport Authority. An option, but an expensive one.
Taxis are available in front of the arrivals area.
The Stansted Skytrain runs from the airport to Liverpool Street Station in London. From Liverpool Street Station you can take a taxi or the Underground to your final destination. You can also take trains from Stansted Station to the north of England, to places such as Cambridge, Peterborough, Birmingham, Manchester, and Liverpool. BUS National Express offers bus service five times a day, Monday through Saturday, to Victoria Coach Station. If your destination is near Victoria Station, this is a convenient option.