is there a bus from lisbon to fatima and back? going there this coming may 2008.
There are frequent busses. It takes about 1-1/2 hours. You can find the schedule and fare information here:
http://www.rede-expressos.pt/0010.asp
If you are planning on visiting Fatima on May 13th (the day of the Virgin of Fatima), do book in advance as chances are most hotels/hostals will be booked solid.
To get from Lisbon to Fàtima, I believe you have to go thru Nazarè.