Hi Robbie:
My bad on the one "F", as you say, you can find it both ways on the net and ÖFFAG is the correct spelling for the whole title.
As to the different letters, I cannot explain the whole story but different languages obviously use different letters, usually fairly similar "special" letters will be found in language "groups" as I call them.
In any case, I use the program below to put in the proper "special" letters when I am not too lazy. In the case when I am too lazy, I use the same method Wendax used where you put in a phonetic spelling. The Ö is usually pronounced sort of like "Er" in English or Spanish.
There is probably a site that lists phonetic spellings on the net but having lived in Sweden and worked so long for Swedish companies I just seem to remember them as I need them.
Anyway, here is the program.
Bill
http://www.vistawide.com/languages/typing_foreign_language_characters.htm