BirdBase is a program that lets you record your sightings of birds, it was designed for professional twitchers. It has a list containing all the species of bird in the world (based on Clement's "Checklist of the Birds of the World".)
BirdArea is a complementary program that lists the range of every species in BirdBase. There is an addon to BirdBase that lists all known subspecies, and another addon that lists every Mammals Species.
There are also a number of reporting functions for listing what you have and haven't seen for various areas.
I've only just started using it and was hoping to get opinions from others who might be using the program too. I plan on setting up two separate databases - one for birds seen in the wild, and one for those seen in zoos.
@Kufri Zoo India: this software would be no good for record-keeping in a zoo, if that's what you were thinking. But if you are a twitcher, then you may find it useful.
Hix