On the Intracto blog there's a new article posted from Jeroen Moons with some suggestions you can use to pay down technical debt in your legacy code through a bit of effective refactoring.

I have good news for you! Squirrels plant thousands of new trees every year by simply forgetting where they leave their acorns. Also: your project can be saved.

No matter how awful a muddy legacy code mess your boss has bravely volunteered for you to deal with, there is a way out of the mire. There will be twists and turns along the way, and a monster behind every other tree. But, one step at a time, you will get there.

He gives lost of different suggestions for things that can be done to "save your code" and make it not only easier to maintain but more flexible:

• Persuading the customer
• Don't replace [a huge mess] with a new one
• Make problems visible
• Fight what hurts most
• Build a library

There's plenty more great suggestions here too with some thoughts and methods to back them up and help you accomplish them in your own code. If you're suffering through a large legacy codebase from day to day, I highly recommend reading through this article.