Explorer Suite is awesome, here is their description:
A freeware suite of tools including a PE editor called CFF Explorer and a process viewer. The PE editor has full support for PE32/64. Special fields description and modification (.NET supported), utilities, rebuilder, hex editor, import adder, signature scanner, signature manager, extension support, scripting, disassembler, dependency walker etc. First PE editor with support for .NET internal structures. Resource Editor (Windows Vista icons supported) capable of handling .NET manifest resources. The suite is available for x86, x64 and Itanium.