Web standards - more than just 'table-free sites'
The term web standards can mean different things to different people. For some, it is 'table-free sites', for others it is 'using valid code'. However, web standards are much broader than that. A site built to web standards should adhere to standards (HTML, XHTML, XML, CSS, XSLT, DOM, MathML, SVG etc) and pursue best practices (valid code, accessible code, semantically correct code, user-friendly URLs etc).
In other words, a site built to web standards should ideally be lean, clean, CSS-based, accessible, usable and search engine friendly.
XSL(T) can be used for organizing large trees of XML so that anyone can read it. For instance a Google Search Appliance serves up queries as XML. For that XML to be read by a general user some transformation has to occur. This is where XSL(T) plays a vital role. It could also be used to style an RSS feed page since the source is all in XML. It is also used as the main templating language for Autonomy's Teamsite (EMS) and such open source CMSs as Symphony.