20 - 25 Lower Barrens - Stonetalon - Ashenvale - Hillsbrad

25-30 Ashenvale - Hillsbrad Dun Garok - 1k needles - lvl 28 -30 shimmering flats

30-35 Desolace - Scarlet Monastary - Strangle Thorn - Stonard - Dustwallow marsh

that should keep you busy for a while