How do I get an effect like that?

Heya...

I was wondering if some of you might maybe able to help me... I am wondering for a while now how to get an effect like this on icons:



I mostly mean the "fact" that the icons have some kind of fog/haze on them which makes them look a bit "used"... I'd love to know how this works...

Icon #1 and #2 are by tardis_mafia & icon #3 is from sightsee

Thanks in advance! =D

I'm using a very old version of Photoshop (Photoshop CS)