Check out these excellent websites that offer W3 standard-compliant website templates and flash template pages for free download without any registration or sign-up!

Simavera Website Templates

Flash and web site templates. Great collection with some attractive and modern designs to choose from.

Open Designs

XHTML and CSS based free web design templates. Over 1100 open source designs available for download and growing by the day!

Tristar Web Design

Just 9 templates here but if your looking for free fast loading quality XHTML & CSS templates, this site is a must!

Solucija

Free XHTML/CSS website templates available to use without any limitations. They can be used on a non commercial site as well as on a commercial one. Keeping a small credit link in the footer is not obligatory. All templates are hand coded and lightweight (under 60KB) which ensures fast loading.

Styleshout

Large collection of quality free website templates for download. All templates are valid xthml(strict) and valid CSS, and distributed under a Creative Commons Attribution 2.5 license

Dream Template

334 free templates but users must at all times have the pre-installed DreamTemplate linking button/text on the front page of their web site. This policy does NOT apply to registered/paid members.