There isn’t much in the way of rigging examples in Houdini, but that doesn’t mean that they are nonexistent.
Side Effect’s Houdini allows for procedural workflow which makes it great for all kinds of effects and simulation. Procedural workflow is also well suited towards character rigging as well.
Bjørn Blaabjerg Sørensen has an introductory look at some basic rigging concepts within SideFX Houdini. Bjørn shows how to set up a simple IK leg on a character.