Following are some of the traditional hobby game manufacturers who have products released for the iOS platform (iPod, iPhone, iPad).  As I become aware of others they will be added to this list.

Bent Castle Workshop

• Numbers League:  They are currently working on bringing this to the iOS platform.

Cheapass Games:

• Button Men: The tabletop strategy game reproduced as an iPhone title.

Days of Wonder:

• Small World: Their board game brought to the iPad.

Fantasy Flight Games:

• Arkham Horror Toolkit:  The "ultimate accessory: for the Arkham Horror board game.
• WFRP Toolkit:  A toolkit for the Warhammer Fantasy Roleplay game.

Slitherine Software UK Ltd.:

• HISTORY™ Egypt Engineering an Empire: This game allows players to build their own empire from the ground up, in ancient Egypt.

Steve Jackson Games:

• Zombie Dice:  This is the tabletop game brought to the iPhone/iPad for free.
• Munchin Level Counter:  A simple way to keep track of your level in the Munchkin card game. Includes a free once-per-game bonus.  (It is NOT the actual game.)
• Fnorder:  Brings you messages from the Illuminati.