Online Tools

SQL Fiddle:

Tools che permette di creare online un DB MySql e sperimentare query sql:
http://sqlfiddle.com/

Regex

Siti web dove poter testare online le regular expressions:
http://gskinner.com/RegExr/?32jsn
http://www.rubular.com/
http://www.regexplanet.com/advanced/java/index.html

XPath

This uses xPath 2.0 but has problem with IE9
http://www.xpathtester.com/

This is nice but uses xPath 1.0 and doesn't work on IE9:
http://chris.photobooks.com/xml/default.htm

XSLT
http://www.shell-tools.net/index.php?op=xslt
http://www.online-toolz.com/
http://www.w3schools.com/xsl/