Here is a list of web sites with useful visual representations of layer blending modes:

"Blending Modes"
http://www.thinkdan.com/tutorials/photoshop/blendingmodes/

"Advanced Layer Blending in Photoshop 6"
http://www.creativepro.com/story/feature/14198.html

"Blending ranges - advanced blending options"
http://www.adobe.com/support/techguides/photoshop
    /advancedblending/blending_range/main.html

If you have an Adobe ID then try this:

"Become a layer-blending expert"
http://studio.adobe.com/learn/tips/phs7advblend/main.html