From Ireland you could mention what became known as Celtic Rock and proponents would be people like Gay & Terry Woods who were members of the original Steeleye Span line-up, until there was a row over politics and they left in a huff, but later had their own band (The Woods Band). Terry went on to join the Pogues in the 90s and is still around the London Irish music scene. Gay (his ex-wife) later formed a band called Auto-da-Fe.

Horslips were huge in the 70s and early 80s in Ireland with a brand of Celtic Rock. Christy Moore had an electric band in the mid 70s (Whatever Tickles Your Fancy Album) and later wend on to found Moving Hearts (with Donal Lunny, Declan Sinnot et al). There was a thread about them here a while back.

If your looking for Folk influenced rock bands check out Traffic, Jethro Tull and even Led Zeppelin to some extent (There's a very folky feel to Stairway to Heaven for example). In Tua Nua were an Irish Rock band which featured uileann pipes and fiddle. Steve Wickham who was their fiddle player did some stuff with U2 and went on to play with the Waterboys (you know the fiddle riff from the start of Fisherman's Blues?).

Incidentally In Tua Nua were managed by Louis Walsh, who now manages boy and girl bands (one of the judges on Pop Stars). Are/were Boyzone a folk-rock band ??? He also set up a trad. based boy band (I'm not joking) called Reel, but they haven't had huge chart success. Younger folkie bands in the UK could be labelled this way as well Equation, Tarras and some of Eliza Carthy's stuff comes to mind.

Some of the stuff being done by Sharon Shannon falls into this department (She was a Waterboy/girl for a while in the 80s as well). And check out Davy Spillane who was a Moving Heart for a while who did some very interesting trad/country/rock cross-over stuff with his own band afterwards.

Donal Lunny has been involved in a lot of this stuff over the years, I don't know if I'd call the Bothy Band folk rock, but it had that type of energy. Moving Hearts and his most recent band Coolfin are worth a mention.

As people have said above, its another one of those marketing terms (Like "Celtic Music") and it means a lot of different things to different people. The US definition and those on this side of the Atlantic are very different Animals (another band worth a mention).