I think all of my sites use DataAssist in some way shape or form but some of the main ones:
SOJO web - this is actually a marriage between DataAssist and PowerCMS extending both to great lengths.
Mix 107.9, Salt Lake - uses DataAssist and much more.
Playful Pooch Dog Boarding, Denver - uses DataAssist to handle content plus to dynamically control page titles and keywords, as well as, dynamically generated head code.