How do you know about/find all these bundles?

This thread contains links to all sorts of bundles.

The extended Steam community. By this, I mean Steam users posting on sites outside of the Steam community and forums.

Word of mouth mostly.

There's a twitter feed that keeps track of a lot of them. https://twitter.com/#!/BundleTracker

I'm with you tritian. I find about them from posts on this forum.

I pretty much find out about them through forums, and enthusiast blogs.

I heard about the HIB from a friend :D I was pretty sad when I found out about the cool ones before HIB#(that's when I heard of it) :(