TextPad is a general purpose editor for plain text files. Many features!

Notepad++ is a free source code editor and Notepad replacement that supports several languages (syntax highlighting).

Tiny hexer is a free of charge hex editor for binary files. It will allow you to edit multiple files (mdi), sectors of disks and other data media (disk editor) and modifiy virtual memory of other processes. tiny hexer is scriptable, lets youview data structures in a special browser in human readable format and has a plugin interface for third party extensions.

Gobby is a free collaborative editor supporting multiple documents in one session and a multi-user chat.

Crimson Editor is a professional source code editor for Windows.