World Coin Price Book

NGC offers a free online price catalog. However, it is not as fast to use as a physical catalog is.

http://www.ngccoin.com/price-guide/world/

Many libraries stock recent world coin price guides. The price of getting a library card will probably be significantly less than the price of a new catalog (they usually go for almost $100).

And, of course, CCF is available for your use - take good pictures and post them in our Identification forum!

I have six volumes of KM World Coins, including the specialist World Gold Coins and World Crowns and Thalers. Together they cover the last 400 years.
Also have Coincraft English and U.K. Coins, 1066 to date, also published in association with KM Publications. (Seven telephone sized books in all).

They are not the most recent editions, but I supplement them with occasional referece to the NGC site World Coin Values. Current prices for all milled and modern English and British coins can be found on Tony Clayton's website.

U.S. Coin Digest (another KM publication), plus on line price reference for American coins OK for my needs.

For current prices of coins of more than 400 years old, my 'go to' site is VCOINS. Approx. more than $30 million worth of ancient coins for sale at any one time, from most of the important dealers across the World.

That covers just about all of current coin pricing with good picture reference for all of them, for the whole of numismatics, over the last 2,500 years. !

For picture reference only, I find Google Images very useful, but you have to have some idea of what you are looking for, and be reasonably intuitive in your search.