A year ago I told you about a webinar on grid systems presented by Mark Boulton and Khoi Vinh. It explained the practicality of grids in web design and how they can tame content-rich sites. You can download the presentation slides here.
Decembers RotM is Nathan Smiths 960 Grid System website. You can download 12 and 16-column templates (based on a 960 pixel-wide grid) for several image and web applications, as well as a CSS framework with HTML demo. The site also displays some example sites (with grid overlays) built using the templates.
If you want to play with an online grid builder based on the same 960px width, try gridr buildrrr. It lets you try out different column configurations as well as some draggable box elements.