Hi,
 
Here I include a tool for beginner. It is a PS file. Print it and you will
get 2 circles, one bigger than the other. Put the small circle on top of the
other. The large circle contain the 12 notes. The smaller 12 numbers :
 
        I ii II iii III IV IV+/Vo V V+/vi VI/VIIo vii VII
 
And the name of the interval from the tonic (i.e. I).
 
You get it ? By turning the circle you'll be able to find chords formations.
 
let take two examples : 
 
1)
        say you want to find what notes compose a Dmaj7, you should
        know that the formula for Dmaj7 is : I III V VII
 
        then turn the I (smaller circle) to be in front of the D
        (second circle) then read the note above I III V VII.
 
2)
        say you have 3 notes D G Bb to find the name of this chord :
 
        - put the I in front of the D then try to find a pattern that
          you know
 
        - put the G in front of the I then you find that Bb is in front of iii
          and D in front of V .. Yes, it's a Gm
 
        - ...
 
 
Hope with these small examples you get the idea.
 
Let me know of any improvment,
Pascal.
obry@flash.bellcore.com