The transliteration of Å is usually "AA". In fact the "circle" above the A is really a lower case "a". It's just that as time passed, it "devolved" into a circle.
I always thought it was "oa". As in boat vs båt (the swedish word for boat). It is pronounced kinda like "oa", essentially a big round long "o" sound with the mouth muscles relaxing just before the sound is completed, making an OOO-a sound.
