I'll begin by mentioning the Holographic Principle, which I find most intriguing at the moment. I've known about it for some time but keep stumbling upon interesting implications.
One of the things conjectured as part of the Holographic principle is that a black hole represents the state of maximum possible entropy in a given region. The way I understand it is that one implication, due to the relationship between information and entropy, is that you can only pack so much information into a region of space before it forms a black hole. It also has implications for the amount of information our universe (which is bounded by a cosmological horizon) can contain.