Lately I've mostly been listening to more upbeat stuff (though with a good mix of slow songs, too...fast gets tiring after awhile!) - bands like Silly Wizard (Scotland), Patrick Street (Ireland), the Bothy Band (Ireland), and Reeltime, which is Irish but plays a mix of tunes - I like them a lot!
I like the Bothy Band and Planxty. Both were featured on the folk show we used to hear in NJ. That was our first real intro to Celtic and British folk music. We enjoyed Steeleye Span and Clannad, but liked the mostly instrumental stuff too.