Recently I have discovered Raphael JS, which has got me excited about SVG once again after years of neglecting the technology. The main issue with actually using SVG on the Internet is that Internet Explorer does not support it, and as it is still (stubbornly) the most widely used web browser, SVG on your website will not render for the majority of your visitors.
Raphael JS works around this limitation by rendering alternative graphics in the VML format for Internet Explorer, and SVG for all modern browsers. Check out the cool demos here:
Updated 2021 : note that the above post is from 2009, but is left here for archival purposes. I have updated the external link to point to the new website for Raphael JS.