I was assigned to extend (and eventually maintain) a legacy system (mostly procedural, semi-ball of mud) without MVC.  Any tips or suggestions for me going forward? :S
Tips on develop further on a legacy system?
refactoring;legacy
Start writing test for the code now, before you make changes. This gives you a baseline of the current functionality. You are going to have a hard enough time figuring out how to add in new features, you don't want to be spending time figuring out how what you did broke something. And that is if you find out you broke it.The automated test will give you some semblance of confidence with the current state of things. It may even indicate a few things that don't work as expected now. But most importantly, it will tell you immediately when you did something that breaks something else. If a test fails after you check in a change, you will know where you changed things and where to look for issues.Beyond that, get as much historical information as possible. If the last person who owned the code is still there, get as much information out of their head as possible. Hopefully the code is commented and there is documentation.