Online programming editors/debuggers are getting popular. Here are the couple of them which I use from time to time:
- IDEOne – a broad choice of programming languages (there is even BrainF**k, however, there is no XSLT)
- XML Playground – another cool IDE for XSL templates. Unfortunately it doesn’t support XSLT 2.0
- Rubular – IDE for checking regular expression written in Ruby
- XSLTTest – Small and neat application for XSLT. Supports XSLT 2.0.