Check Indian Railway Availability Calendar
Cleartrip seems to be adding bells and whistles into its online booking portal. They had launched Indian railway booking, train schedule feature recently and now they have launched a new feature called ClearTrip Calendar.
Cleartrip calendar is an Indian Railway availability calendar where you can find out the trains availability From point A to Point B for next 15 days. Search results are colour coded and available dates are highlighted in green.
Here is how it works. You select your From (city/station) and To(city/station), travel class and dates preferences and hit search. This will bring you a calendar view of the date ranges with the available trains and the number of seats availability with color codes.
Cleartrip calendar is a product of Cleartrip's research and I am not sure how accurate it is. Cleartrip had launched ClearTrip Graphs in the past and I amn not sure whey those graphs links are off the site. I was able to digg my older post that explains how to Find Cheapest Airline Tickets in India and found out that Cleartrip graphs are still there but not sure about the accuracy.
So if you are planning to travel by train and before you buy your cheap train ticket, you might want to look into the availability. This can be a nice tool for planning your next train trip provided that Cleartrip keeps it alive.