its best to run seperate lines and may be against code to hook a bathroom fan and a dryer to the same vent esp if the dryer is gas. these would probably work but be aware that they dont seal 100% so you might have a bathroom that smells like a dryer sometimes and a dryer that smells like a bathroom.
http://www.rewci.com/4dusplobadar.html#
http://www.rewci.com/4dusplobadar.html#