I've been finding all sorts of tips like this all of a sudden. Maybe I should take the time to read through the CS3 bible Thoroughly instead of skipping around and skimming bits here and there
for example:
Press Shift+[
(Shift+left bracket) to make the brush softer; press Shift+] (Shift+right bracket) to make the brush
harder. Both shortcuts work in 25-percent increments. For example, you have to press Shift+] four
times to go from 0 percent Hardness to 100 percent.
Preset shortcuts:
You can cycle between presets even when no palette is visible. Press the
comma (,) to toggle to the previous brush shape in the list. Press the period (.) to select
the next brush shape. You also can press Shift+, (comma) to select the first brush shape
in the list (1 pixel wide) and Shift+. (period) to select the last brush.