I'm glad you enjoyed Tempest, I was the one who posted the album in the mediafire thread. They are one of my favorites bands, I think I've seen them live about 5-6 times, if not more. Usually see them at least once or twice a year. I avoided doing a big discog post in the thread, but I'll post another one of their albums soon.
Besides the bands already covered, I recommend Real McKenzies. They are like Dropkick Murphys but Scottish instead of Irish. The Skels are also nice. And Amadan, who are bit more folky.
And if you want to get really out there, try some Celtic ska, The Trojans