Play around with this site to find the cheapest fares:

http://www.flylc.com/directall-en.asp

Keep in mind that instead of flying out of Florence, you might be able to choose Pisa or Bologna as departure points. Rome might also be just as convenient as Venice.

1.flying euroeconoair always cheaper skyscanner.net
sales very cheap booked in advence pack light decline seat
if you want to save.One super cheap way I have done it
easyjet.com CDG MXP(Milano) 30 euro then cheap regional
train 10 euro to venice-tourism.

2.cheap train to ROM then fly Barcelona vueling for me cheap
in past out of Rome will be cheapest.

3.Flying is your best bet... Have taken the Talgo Med to
Montpeller nice train not cheap then Paris on TGV.

4.barecelona30.com best apt site for me.

Have fun!
seat61.com for train info.

There's a sleeper train taht departs Venice (Santa Lucia station) at 19:57 and arrives the next morning at 9:16 at Paris (Bercy station). There is no need to change trains and the journey is 13:19 hours long.

You can play around with the train schedules on bahn.com to see what works out best for you.

Be warned that due to industrial actions by some Italian train unions that the Venice (and Rome, florence) to Italy Artesia trains can be very dicey - trains hours late - not cleaned, etc. I would not advise taking that train during the next two months.

Yes there is a day train from Barcelona to Paris - it actually leaves from Figueras, about an hour or so by rail north of Barcelona - then French TGVs directly to France and connections to Paris.

Great train info - www.seat61.com; ww.budgeteuropetravel.com and www.ricksteves.com.

Also check for flights between Pisa (not far from Florence) and Barcelona.

Girona Airport serves some budget flights and it is only an hour or so from Barcelona by train or bus.

Vueling flies from Barcelona to Paris for reasonable rates. http://www.vueling.com/EN/

helpful info - bookmarking