http://japanese.about.com/library/weekly/aa070101a.htm

This page talks about the names of the radical positions, as well as the groups of radicals and what they are called.

Regarding the names of radicals in Japanese, I posted a radical / primitive equivalent list in another thread.

Learning the names of radicals takes some time since there are over 200 radicals.

I recommend the DS game "The Kanji Quiz" which let's you train the names for the radicals and learn which part of a kanji is the radical.

The main usage for the names of radicals, outside of academics, is to explain how your name is written. Obviously, this doesn't apply to us westerners, but most Japanese know the names of the parts of the kanji used in their names. For example if you phone some company and they need to write your name, you simply say the names of the parts and how they are connected.