Best Cheapest way to travel from Rome to Athen in august?

Flying will probably not be any more expensive from Rome than the total cost of getting to Athens by ferry since it means a bus or train from Rome to Bari or Brindisi for the ferry, then the ferry across to Patras or Igoumenitsa followed by a bus to Athens. The time all this will take is close to 48 hours by the time you reach Athens compared to a few hours on a plane.

Thanks Lee, that answers my question. Any website for airlines you like to use in that part of Europe?
Thanks in advance.

You might check to see if you can catch a saver fare on Aegean Airlines. With taxes included the cheapest fare will be less than 80 euro one way. Full fare is about 175 euro so anything under that is still a fairly good deal.

http://www.aegeanair.com