Some of the most famous theories about the cosmos are Big Bank Theory and the Inflating Universe. Those are a few of the most modern as is the Multiverse. There are older theories too that are commonly known although they have been disregarded over time like the Cartesian Vortex Universe and the 1548 Polish Copernican Universe.
There will be others added to the list and of that you can be sure of because theories tend to evolve throughout the course of time.