Last week, I came across XML Marker, a free XML editor that is great for simple tasks.  It doesn't have the full range of abilities of a commercial product like Altova XMLSpy or StylusStudio.  I have been using the evaluation versions of these commercial products to do simple XML editing, but I can't justify coughing up $500 for a simple XML Editor.  XML Marker bridges the gap: it doesn't suck like Microsoft's XML Notepad but it give you multiple views of your XML document like the big boys.  I edited the config file for this web site, and it works great.  It doesn't have schema validation built-in, and that would be a nice addition.