"The world's most awesome jQuery slider" by Gilbert Pellegrom, made easily available for WordPress.
The Simple Nivo Slider plugin provides easy access to Gilbert Pellegrom's excellent jQuery-based Nivo Slider. The admin panel makes it easy to tweak the most commonly used Nivo Slider options from within WordPress.
Visit http://nivo.dev7studios.com for more info on the Nivo Slider, that's where the real magic happens.
Valid XHTML 1.0 code generation and CSS stylability are priorities.