I was thinking of taking the night train from Paris to Florence on March 24. The trenitalia website has some great deals, but it looks like they will only ship tickets domestically. Does anyone have any other ideas as to how I could get to Florence cheaply?
Normally I wouldn't think there was a need to book in advance, so long as you appear at the station in plenty of time. However, your date is Easter Monday, and an evening which might be quite busy on the night trains, so you're quite sensible trying to book in advance.
I see you're in the US - in Europe there is a company called:
who we have used. They are more expensive than buying in Italy however.
I would have thought you could have chosen a ticketless option on trenItalia's site - this is where you opt to print your own tickets. Perhaps someone else might advise.
Paris to Florence is quite a long train ride. Have you checked flights? I know it is Easter, but it might be worth investigating. http://www.skyscanner.net
You can also try to book your tickets from http://www.voyages-sncf.com/ This is the French train site and the company you would buy your tickets from if you were to go to the counter in Paris. Check whether they allow you to book in advance and then collect the tickets at the counter in Paris.
t_maia is right - it will be cheaper to go by plane. For price comparisons I use:
http://flightchecker.moneysavingexpert.com/ because the price includes taxes. You can also experiment with the box "Only show prices under ***"
You will then go to the airline and purchase through your own currency, and (usually) print your own boarding pass if you have hand luggage. Remember that cheap airlines have add-on prices for hold luggage, etc, and they don't give you free anythings such as coffees or meals!!
Ryanair is probably your best option - nearest to Paris is Beauvais while nearest to Florence is Pisa. DOn't forget to add coach transfers to your two cities. Good luck!