www.numista.com

this is a very useful site for coin collectors better known as numismatists. If you are a passionate collector of world coins, this site is just for you.

The site is beneficial in 3 ways. It has a fairly large database of world coins, from about 300 countries, mostly with images of the coins and their specifications like weight, dimensions, metal, mintage etc. Also it has a large database of coin collectors who are interested in swapping their doubles coins. Thirdly it helps you maintain an online database of your coins, which automatically computes your doubles coins and helps you to arrange a swap with a likeminded collector.

As a collector, you have the option to use this tool only as an online database for your coins. You need not swap your coins if you are not interested. You can allow or not allow the site to display your coins to those browsing the site. If you are looking for a swap, you can have a lot of data about prospective swappers. Their ratings, number of coins they have for swap and the feedback they have received from their earlier transactions are before your eyes to evaluate.

When you are searching for a particular coin, the site displays data if any member of the site is interested in swapping this coin. Also sometimes if the said coin is available for sale on Ebay, you have a ready link to it. This arrangement gives you the opportunity to buy it if you so desire. Otherwise you get an approximate estimate of the value of the coin. Please note that ebay rates are not always that dependable.

Registration on the site is free and easy to fill up and enroll. All in all, a very useful site for numismatics enthusiasts.