According to Phil Taylor's excellent docuentation for BarFlay:

Although there had been developent of modes for centuries:

Finally, in the 16th century Glarean identified 12 modes and assigned Greek names to them...

To expand on Little Robyn's post (and using the same system), Phil Identifies the following as the 7 "white note" modes:

  Ionian (major)  : C
  Dorian          : D
  Phrygian        : E
  Lydian          : F
  Mixolydian      : G
  Aeolian (minor) : A
  Locrian         : B
  

Phil has given me permission and I'm hoping to have a slightly modified (so as not to read as a Barfly help file) version of his text at folkinfo as a reference within the next couple of months.

Jon