LibrarianLib is the library mod to end all library mods. It doesn't attempt to do much else than take the pain out of modding. It can handle a great deal of boilerplate code that you really shouldn't have to touch. Its largest components are an automatic serialization system, automatic model creation and registration, a powerful GUI library that takes out the magic numbers and complex control stuctures by making everything modular, and a powerful and flexable particle system.
LibrarianLib depends on Shadowfacts' Forgelin. Make sure you have it if you want to use it.