My official Vaticoins page, with 500+ pictures of the coins listed here, bargains, offers and news. Please visit it and give it a big "Like". Buyers that give a "Like" to my page will receive a free coin on their first order.
Numista is probably the best online catalog of world coins and also a great platform for swapping and organizing one's collection.
Another great resource is CoinBrothers, an online user-generated catalog that also offers collectors a platform for selling, swapping and organizing their collection.