Nusmismatic Index

There are many great resources for coins on the internet. While bookmarking sites are cenrtainly useful, I find having a visual representation of these sites is more useful for me.

Ancient Coins

General

This is a great and very comprehensive list of ancient coins. It is particularly useful for identifying Roman Imperial coins. 

Roman

The definative catalogue of Roman Provincial/Greek Imperial coins. The published books contain introductory material which is lacking in the online catalogue. This is still a work in progress.