how to achieve this look?

I've been doing unsuccessful attempts to create icons that end up looking like:



L-R: by teh_indy, neversince, teh_indy, xoashwee, dekolette, misstress_tink

I resize my hi-res images to 100x100 but they don't look as clear as those icons. It's so frustrating! I've tried sharpening, but they don't look as nice--over sharpened images are ugly, yet the ones above (if sharpened) look waaaay better.
I use PS7.

Is there a specific way to achieve the same look when I resize images and make them look like those icons? teh_indy, misstress_tink, dekolette (and another icon maker whose username I can't remember right now so I didn't provide a sample icon) do it so well! How to achieve the same clarity of images would be perfect.

If anyone can provide a tutorial or give some tips, please do so (for PS7)

Thank you :)