Notepad++ is a free (as in "free speech" and also as in "free beer") source code editor and Notepad replacement that supports several languages.
I have been using Notepad++ for several months. It works well for editing XML as well as source code and plain text. Looks like it can go well beyond basic editing too. There are many features and plug-ins that I have not explored.
Note-to-self: Hold Alt+Shift to enable column selection mode.