Irctc.co.in is one of the best website that I came across till now as it saves much time in booking tickets. This irctc.co.in is maintained by Government of India. This site is very useful in booking train tickets especially from home itself.
To book a ticket you need just register in irctc.co.in website and you will receive your registration confirmation through mail containing a username and password to your account and using which you can login into the site. I have booked the ticket recently from chennai to hyderabad and need to select the date of journey and select the available trains and based on seat availablity you can book the tickets.