MisterFiber - Original developer for 2 months, concept.
TDWP_FTW - Some graphics, many ideas, blocks, some biomes.
ScottKillen - Saviour of original mod, technical support, buddy.

Shout out to:
BlacksWhites - Idea for Wasteland.
MindKrafter - Idea for Marsh.
Exalm - Continuing development of the original ExtraBiomes.
HarpSeal - Cool guy.
toughenough6 - First post on original topic.
paull105 (AKA, SirDerpingtons) - First video showcase of ExtraBiomes.
Ancetras - Love that texture pack.
851853 - Giving MisterFiber an awesome laugh for 2 days (http://i.imgur.com/DuKHu.png)
Delocuro - textures for biome colored leaves.
SirSengir - For providing a great example of a simple yet powerful API
Eloraam - For graciously providing help with RedPower integration

The Buildcraft Development Team
  Extrabiomes XL uses a modified version of OilPopulate.java from BuildCraft.
  The modified source is available here: http://www.mediafire.com/?71rdlcs12d1l2ni
  BuildCraft is distributed under the Minecraft Mod Public License 1.0 at
  https://github.com/SirSengir/BuildCraft/