Blend Mode Keyboard Shortcuts
I never used to use keyboard shortcuts for blend modes. Then about a year or so ago, I realized that the keyboard shortcuts for blend modes are actually very easy. It always involves the Option-Shift ( PC: Alt-Shift ) keys and then one letter that's usually the first letter of the blend mode. For example, Option-Shift-M ( PC: Alt-Shift-M ) is Multiply. The letter O is Overlay. The letter S gets you Screen and so on. It doesn't work for all of them ( F is actually Soft Light ) but it's pretty darn close and since I've started using them I work a lot faster.
Some of them are kind of unintuitive (Shift+Opt+F for Soft Light?), but the whole list of ’em is in the Photoshop CS4 Bible!
Here’s a list: http://quamut.com/quamut/photoshop_cs3_keyboard_shortcuts/page/shortcuts_for_blending_modes.html