Here are link's to Tankspot's guides to all the Ulduar bosses. Many we may know, but there are many who have not seen them yet and here is a good way to get your feet wet in the ULD.

The Siege of Ulduar
Flame Leviathan on Hard Mode
XT-002 Deconstructor (easy mode)
Razorscale (easy mode)
Ingis The Furnace Master

The Antechamber of Ulduar
Kologarn
Auriaya (Crazy Cat Lady)
The Iron Council

We have downed all of the above bosses, and we are working on Freya and the rest. I am posting these here for future reference.

The Keepers of Ulduar
Freya
Mimiron
Thorim
Hodir

The Descent into Madness
General Vezax
Yogg-Saron