Actually, depending on the type of dryer you buy, this isn't the case. To avoid the need for a connection to the outside, you can get a condenser dryer:
"A condenser clothes dryer is a machine that looks just like a conventional tumble clothes dryer, but which does not require an external vent. For the user/owner, operation of both types of dryers is essentially the same - the difference is in the internal design."
http://ths.gardenweb.com/faq/lists/l...958010854.html