A live cd would have any number of target uses. The big name common distro's make them generally for people to see the distro run. Gentoo for example doesn't allow one to use it to install with. Fedora, Ubuntu, OpenSuse and such have a live cd/dvd that can be used like a common distro and also be used to install.
The web lists of live cd's might be current with 100 or more live cd's. Each one has it's uses. How many versions of Knoppix are there out there and the derivatives of the clones like Puppies.
This list used to be my go to list. http://www.livecdlist.com/
but it isn't complete.