This style for Google Calendar hides the #nav bar on the left-hand side of the calendar grid until you hover your mouse cursor over the "hover bar" (see the screenshot below).

The width of the hover bar is, of course, customizable--you just have to edit the code to suit your preference. I've set it to 25px as the default--rather wide. You can set it as low as 5px without losing part of the pointer image. With a narrow bar you can move the mouse cursor across the bar quickly enough to not cause the nav bar to display; for a narrow bar the "suggested" method for causing the nav bar to display is to move the cursor to the left of the window (quickly) and then bring it back into the window (not quickly) instead of trying to position the cursor precisely over the bar. FWIW, Calendar's right-hand side toggle bar (for the Tasks/gadget panel) is 10px when it's "closed", which is what my hover bar is currently set to (after some playing around with it), but, TEHO.

Updates...
09Jul2010: updated for Google Chrome to correct the gradient background at the bottom of the nav bar--was dark blue, is now light blue (of course [as usual], Chrome is slower to render CSS converted into a "non-native javascript extension" than it is when rendering just CSS--guess that's why I've been converting some of my styles into "native CSS extensions" for Chrome [they're faster :D]... will do the same for this one soon enough)

The 'Before' image is before the hover; the 'After' image is after the hover.

Here are a couple more images with the nav bar hidden/not hidden:
http://img822.imageshack.us/img822/7518/gcalmultiweekgridaio12j.png (w/10px hover bar)
http://img708.imageshack.us/img708/2585/gcalmultidayweekgrid2ai.png