Theres been talk about getting people their onyxia key. Heres the steps in order. The level requirement is the same as UBRS which I think is 58+. These are not all the quests just the major steps. There are also some short or easy quests in between I'm not bothering with since they can be solo'd.
1) Warlord's Command - Picked up at Kargath. Have to kill 3 bosses in LBRS and find the document's there that randomly spawn at one of them. Has to be done in a 5 man party. Quest NPC then gives you rewards and sends you to speak with Trall's Advisor in Ogrimmer who gives you another quest to Speak to Thrall.
2) For The Horde! - Given by Thrall in Ogrimmer. He sends you to UBRS to kill Rend. Can and should be done in a 15 man raid. Take Rends head back to Thrall for the next quest, a city wide buff, and some pretty nice rewards.
3) The Champion of the Horde - Thrall will babble at you for a bit then send you to find Rexxar. This is more irritating than hard and can easily be accomplished solo. I only mention this step because he wanders and sometimes takes a bit to locate. Here's his path: Desolace, Feralas
He sends you to a NPC in western plaugelands who is fairly easy to find - Myranda the Hag
4) Ocullus Illusions - Myranda the Hag in WP sends you to UBRS to collect 20 dragon eyes. They drop from the dragon spawn there and can be collected in a raid. Once bring the eyes to her, she'll send you to emberstrife in dustwallow marsh with a amulet.
5) The dragons - You'll get 4 quests to kill 4 named dragons from the different flights for Emberstrife. Scryer in Winterspring, Somnus in Swamp of Sorrows, Chronalis in Tanaris, Axtroz in Grim Batol.
6) The General - You'll take a amulet emberstrife gives you to rexxar who will tell you to get a drop of blood from General Drakkisath in UBRS. And since the general is likely pretty fond of all his drops of blood you'll have to kill him for it. I think most of our members close to 60 have been along for a UBRS raid so this won't be to big a problem. Return it to Rexxar for this Drakefire Amulet aka the key to onyxia's lair.
7) Victory! - dance naked in front of the Ogrimmer bank and have everyone bow to you for your accomplishment of completing one of the more irritating quest lines in the game.
My descriptions for the quests may have some errors in it so please correct me or add something if I missed it. If you want to read through every quest your self then go to here: Onyxia Key Quest Start and keep clicking on “Leads to” on the left side.