I will be traveling from Portrush to Galway in June, most likely via Derry. I am looking for interesting sight seeing opportunities on the way to Galway. I am not necessarily set on going to Derry, so if someone has a better idea, I'm all ears!
Maybe the Ulster American Folk Park? Ulster American Folk Park
We drove that way in April, 2012. There were several interesting neolithic sites just outside Sligo (Carrowkeel, Carrowmore) and Yeats grave is worth a brief stop. We detoured to Ceide Fields which is interesting if you are really into neolithic sites. Otherwise, I would suggest using the time to explore Connemara which is jaw-droppingly beautiful, especially on a day with an atmospheric sky. Clifden and Roundstone are both charming. Also take some time to drive the Famine Road over by Delphi. Before leaving Donegal, we drove over to Derry and walked the walls around the city. This was interesting but not a highlight. Have you considered exploring County Donegal? It has some beautiful peninsulas and Donegal town has several good restaurants / pubs.
I would recommend making a stop in Derry - I spent three days there last spring, and would visit again. And it is the UK City of Culture for 2013, so I'm sure there will be lots of things going on. If you are at all interested in learning about the conflict in Northern Ireland, definitely visit the Museum of Free Derry.
My information is dated since I was there in 2002, However, I believe most of these things are still available: We have never regretted going to Derry. We only spent a few hours there, but took a walking tour that was very informative and made the visit very meaningful. We enjoyed the Beleek area. I really wanted to do the Beleek factory tour. I am not sure how much that would appeal to you. We stayed one night in Westport. While there we visited some pubs for music. But the highlight was climbing Croagh Patrick. Great hike! We also enjoyed the Connemara scenery and towns and stopped in Kylemore Abbey. We took 3 days to do all this spending a night in Westport and a night in Ballyshannon. Have a great trip!
Since you are up north, I would reccomend visiting Slieve League in Donegal. These cliffs are amazing and I found them better than the Cliffs of Moher. Slieve League can be a challenge to get to (country roads, not the best signs). You can either park at the base and walk up the road to the top through winding driveway, or drive up to the top. By walking you can really enjoy the amazing views and not concentrate on other cars or the turns.