There are many sites that list the syntax of XSLT and XPath. They aren't particularly a good way to learn the language, as they just list the various functions and elements. The w3schools site also has the serious defect that it lumps together functions from XPath 1.0 and 2.0 without identifying which are which. So if you're using XPath 1.0 (like almost everyone at the moment) you can waste a lot of time trying to use functions from 2.0.
The "bible" of processing XML with Java is Harold's book - which has been placed online. There is a chapter on XSLT. For XSLT I use Michael Kay's XSLT Programmer's Reference - - ieee, now in the third edition, another book to the wish list.