How do Chaos people do it? Are there fallen Navigator Houses? Is every Chaos Voidship a daemon engine? Can Sorcerers navigate the Warp through some arcane means? I'm not finding anything in crunch or fluff. Please help!

The Navis Primer, a supplement for Rogue Trader, has some fluff (and stats) regarding Warp Guides, men and women (and others) who use various and sundry esoteric means of guiding vessels through the warp. An example- using Forbidden Lore (Daemonology and Warp), a Warp Guide might entreat Immaterial entities to "carry" or guide the vessel to its intended destination, though these entities may require a sacrifice, and even then there is no guarantee they won't take a detour along the way and have a bit of fun terrorizing the vessel and her occupants. A Warp Guide might also use an artifact attuned to the warp, akin to a divining rod, or read the course of the journey in spilled entrails.

I'm pretty sure I've read how non-imperials do it somewhere (basically the same, just more brutal and magicy), most likely some small box or something in Navis Primer (which has the basics, anyway).

Sacrifices,

Lets not forget sacrifices to the Dark Gods!

There are traitor (or enslaved) navigators - you see one in the Aaron Dembski-Bowden Night Lords series ( Soul Hunter, etc).

However, you don't necessarily need a navigator per se. Sufficiently gifted sorcerors are able to navigate the warp; Zaphariston is said to do this for Abbadon, and I imagine Ahriman is perfectly capable of steering his own flagship.

Bound daemons (and I guess daemon engines) would also work.

Essentially, a sufficiently high Forbidden Lore (Warp) skill probably includes the ability to guide a ship.

The Navis Primer, a supplement for Rogue Trader, has some fluff (and stats) regarding Warp Guides, men and women (and others) who use various and sundry esoteric means of guiding vessels through the warp.

At one point, I wrote out their Blood Sacrifice Talent as a talent for BC.

Tier 3 Undivided.

Isn't there a warp navigation skill in the black crusade core rulebook?

Yup,

P. 105.

it doesn't explain exactly how it works though.