Cork is a great place to use as a base if you want to travel further afield, and you needn't hire a car to travel to other towns as the bus and rail services are pretty good. I used two websites to help plan our journeys before we travelled:
It's very expensive to get a train between Dublin and Cork if you dont have any discount pass. A return ticket was about £40 punts and the train gets very packed and uncomfortable. I've often had to get this train from Limerick Junction and had to sit in the carraige all the way to Dublin. Not nice. So I got a car. :)
AFAIK it's now €50 rtn (adult) between Dublin & Cork
Finally Irish Rail has moved with the times. The title of this piece is their current by-line which doesn't realy instil confidence in their ability to get you to your destination on time or even in one piece. But like they say... they are getting there.
In the last few years they have introduced new trains with wheelchair-accessible toilets and data blast announcements. There is a train now every hour each way and they always depart on time and even sometimes arrive on time too. They have also started an online booking service which is efficient and a great way to save on transport costs too.
Okay so here is the low-down. BOOK YOUR TICKETS ONLINE!! If you buy your ticket at the station you will pay anything from €56 for a single Cork/Dublin to upwards form €72+ for a return. Online you can buy tickets for as little as 10€ one way! You will need a Laser or Credit Card. (however you pay a scandelous €3 surcharge to use your credit card!) The easiest way to pick up your ticket at the main stations is to bring the card you booked with and swipe it at the automated ticket pick-up machines in the main concourses. It is a very wise however to print off your receipt or to take down your booking number, as somtimes these can be out of order.
To be honest the train is the only way to go. Its comfortable, fast and conveniant.
Getting to Cobh is most convenient by car. Follow the directions from the City of Cork. More fun is to take the historic railway that used to connect the city of Cork with Cobh. Admission price.
The town is walkable.