I've created a website which tracks values for numerous crypto-currencies and allows you to view these in a configurable chart.
Data is gathered once a day and I hope that with some time long term trends will become visible.
Underneath the chart is a table showing the latest gathered information and a calculator to get the current value in usd, euro or gbp of a crypto-currency portfolio.
http://www.cryptocurrencychart.com/Data gathering started on 11th of November 2013, so not that much information yet.
I hope the site is of use to others and would love to hear tips, remarks or anything else you have to say about the site.
Some technical detailsI'm using the YUI3 JavaScript library (the chart is also from this library)
Settings (chart value, current date, visible coins, scale, my coins) are stored in HTML5 localStorage if available and in cookies if it is not
"My coins" numbers are never used server side, all calculations take place on the client using JavaScript (even if no localStorage is available and the numbers are sent to the server as cookie)
The chart point interval is changed automatically depending on the date range selected to prevent slow loading/overloading the server (is mostly for later when there is more data)
Using Google Analytics to keep track of visitors