If you are a developer on the Windows platform you may have used or encountered Notepad++, if not you should look it up. Notepad++ adds many IDE like features like syntax highlighting, code completion and macros in a lightweight package that should replace windows notepad.
If you have ever complained about programs generating ugly XML you should install XML tools for Notepad++. The tools are installed from the plugin manager and give you a whole list of tools including Pretty Print, linearize and toggle the HTML identities (< to <, etc). I regularly copy blocks of code from SharePoint/SharePoint Designer into Notepad++ just so I can read the stuff.
XML is like violence, If it is not doing what you need it to do, you are not using it enough. 
