A List Apart: Articles: Accessible Data Visualization with Web Standards
Wilson Miner has written a fantastic article for A List Apart discussing how he built the text and CSS-based charts for the fantastic data representation on EveryBlock. Whilst it's simple and really only going to be useful for barchart variants, it seems to me to be a great way to visualise data using basic technologies.
http://www.alistapart.com/articles/accessibledatavisualization