FirstObject XML Editor
I was looking for a fast, free XML editor today, which could handle fairly large (~100MB) XML files without too much hassle. Previously I’ve used XML Marker for this; it’s fantastic, however it has a fairly clunky interface. I wish SymbolClick would release a more modern version!
Anyway, today I found FirstObject XML Editor and gave it a try; so far it seems great! It’s lightweight (only a single EXE file), and it’s fast. Best of all, it has a very, very simple way to format (i.e. pretty print) XML files – just press F8!
Highly recommended.

Have you heard of Liquid XML Editor (http://www.liquid-technologies.com/xml-editor.aspx)? I was an Oxygen user but then moved to Liquid because it was a little bit cheaper but also has thes axon engine which is faster for xslt.