Go to the Sins official website and hit up the modding forums, there are alot of posts where the modder puts up links to them.
The "Sins Plus" mod is pretty cool, they add several different types of planets and a couple things to the research tree, nothing major in tech choices just the ability to colonize gas giants or take over broken down ships. In this mod they have planets like oceanic, urban,toxic,industrial,paradise,savanah,swamp and they have ship graveyards laying around that you can send a colony frigate to and take over the broken down ships.
