My dad and I visited the GPO in Dublin last year. Quite interesting. There's a video with actors playing the roles of postal employees and their reactions to the Rising, and also some good dioramas. Unrelated to the Rising is a mini-museum of postal history. Outside is a giant metal spire which stands in place of Nelson's Column and is a lot less impressive - none of the locals we met had anything complimentary to say about it.

We also spent a couple hours in a nearby bar named for one of the ringleaders (Can't remember which - Connolly?) who had spent much of his time there before the war.