I'm wondering if anyone has suggestions on how to travel between Barcelona and Florence. I have researched flights and the overnight train to Milan with a connecting train to Florence and the trains seem to be a about 500 cheaper than the flights for 4 people. The trains we were thinking of using is through Euro Railways but would love any other suggestions. Any helpful tips on traveling between these cities would be much appreciated!!

Have you just looked at flag carriers or have you also looked at budget airlines? It would surprise me if an overnight train would cost less than a budget flight. Check out connections between Florence/Pisa and Barcelona at www.whichbudget.com. Some of the budget airlines have very strict luggage restrictions, but some are more lenient.

If you're looking at cheapest quickest, from 65E for a flight sounds pretty good - http://www.meridiana.it/en/index.aspx

For something more adventurous, why not a train to Toulon and then ferry to Corsica for a look around and then another to Livorno on the Italian coast or possibly even flights between Corsica and Florence - use www.attitudetravel.com

There also the overnight ferry from Barcelona to Livorno (the port cruise ships use for Florence).
http://www.grimaldi-lines.com/