Free XML tools?

[Ted Roche]

So, what are recommended for good Free (as in Freedom) XML editors? 
What kinds of capabilities do they have? I've been using Stylus Studio, 
and the ability to develop XSLT via GUI drag-and-drop matching is 
pretty cool. Also, being able to debug the XSLT "live" as it parses is 
powerful. Are there similar tools for FOSS? Linux, Mac and Windows are 
my main platforms...

Ted Roche
Ted Roche & Associates, LLC
http://www.tedroche.com