GScript Modern (Demotic) Greek typing with a US/European keyboard: includes speed-typing and automatic accents and genders      Free online trial period now available

How to read "Greek ASCII"

Greek resources (fonts, keyboard, news digest, etc)

See also Manuel A. Lopez' informative page on typing Classical Greek in Windows

James Naughton's page on Unicode Classical Greek and his Unicode Greek Inputter (which uses a Beta-code approach) are both highly recommended.