Finding Queries that have been done on a DB

Hello all!
This is my first post!  I am interested in finding out what queries have been made against a particular database in postgres. The version of Postgres is 8.0 running on Mandrake 10.  The queries are made by client computers over the network.  What steps must I take to accomplish such a task?  Is this even at all a feasible goal?

Much Thanks!!!!