I make my icons using PhotoShop CS2 and a good dash of inspiration. Check out my Links/Resources @ lunaestas.com/iconpile for a full list of the resources I use.
OK, here's what you're wondering. No credit is necessary. (Seriously.) That isn't to say that I don't appreciate it when my icons are credited - I most certainly do! - it's just that it isn't something I get worked up about. :) Just use 'em and enjoy 'em!