Liturgica.com – Books and Music
Eighth Day Books – Books plus much more. A good purchasing resource for almost anything.
St. Isaac of Syria Skete – Great source for printed and mounted icons
Holy Transfiguration Monastery Store – Great source for all kinds of religious items including icons, crosses, incense, etc.
St. Herman Press – Books and other
Musica Russica – Russian Music
Light and Life – Large selection of publications
Uncut Mountain Supply – Large selection of icons