There are many ferries to choose from when sailing to and from Paros. Some are extremely large and are cruise ship like while others are much smaller and transfer passengers to Paros from Athens in several hours. Prices range from 50 Euros to over 85 Euros depending on the class of service you choose.
The following site is an excellent source of ferry information including prices, ferry routes and timetables: Greekferries.gr
Ferry Service to and from Paros
The Agapitos Line runs the Super Naias 4 times a week between several islands including Paros.
The Agapitos Line runs the Express Olympia and the Express Apollon between Paros and several other islands several times a day.
The Golden Vergina sails between Piraeus to Paros and other islands twice a week.
GA Ferries owns and runs the Milena. This ferry makes weekly trips between the islands.
Other ferry companies are Minoan Lines and the F/B Marina.