Generally www.bahn.de (German Railways site) is the best for timetables accross Europe. The SNCF (French Railways) site is www.voyages-sncf.fr - may also be useful.
There is a high speed train called "Thalys" that runs from Paris to Brussels and some continue up to Amsterdam - there are probably also slower trains ... travel times are pretty short under 90 mins to Brussels and about 4 hours to Amsterdam.
From a scenery point of view I have never travelled by train on this route - from the air it looks pretty dull though - very flat country so not very scenic compared to the great train journeys of the world !