Here are some videos of 2 of the new Firelands bosses. Alysrazor (25 man) being attempted by the guild Enigma and wowhead fighting Firelord Ragnaros (10 man)!

Alysrazor

Firelord Ragnaros

For some of the best PVE raid guides that are being constantly updated I recommend you check out the World of Warcraft PvE Guide – PvE Formula