I asked this on Quora, and no one answered, so I went ahead and answered my own question after having ridden between the two towns. There’s:
- the ruin of Kells Priory (“one of the largest and most impressive medieval monuments in Ireland”);
- the Rock of Cashel if you take the northerly route, or some nice seaside towns (Dungarvan, Youghal) if you go by the coast;
- The Irish Steam Preservation Society museum with lots of old steam-powered cars and tractors and such.