An anagram is basically a rearrangement of the letters of a word/phrase to produce a new word/phrase. Someone who makes anagrams is an anagrammatist(quite a long word to write or say out loud). The original word/phrase is the subject of the anagram.
Some examples: William Shakespeare = I am a weakish speller OR I'll make a wise phrase; Astronomer = Moon starer; Funeral = Real fun; Dormitory = Dirty room, and many more others.
There are quite a number of Anagram finders online. The first result in the Google search I did was the Internet Anagram Server(I, Rearrangement Servant). Of course, anagram finders like these won't help if you want to form an anagram out of a very long phrase/paragraph.
Here's one anagram from the same website, based on Lord of the Rings:
The Curse of the Ring (from The Lord of the Rings)
In the land of Mordor, where the shadows lie,
One Ring to rule them all,
One Ring to find them,
One Ring to bring them all,
And in the darkness, bind them.
Who fears Nine Morgul men,
A lot of bandit demons,
The gathering torrent,
And Him, one Dark Lord
Sheltered within His hell?
Men, blind to the One Ring.
(by Michael J. Mateyka)
I won't bother to see if all the letters are used correctly... :P
See if you can find some special anagrams! There are anagrams for RI and HCI... :)