For those who would like to make the travel by train, reservations are now available via SNCF (French railway company).
Web site is http://www.voyages-sncf.com/
(language selection is available at the bottom of the home page)
For exemple (I speak for the one I've taken the most!) you can find a travel (Amsterdam / Paris / Amsterdam) for 70€.Be careful, bicycles are allowed in these trains only if they are dismenteled and in a bicycle-bag (or packed in cardboards), which means you can't travel with a big bike!
To prevent any (very) bad surprises, please check previously with your national railway company!
Don't hesitate to ask if informations are not clear enough!