I like Scout 4/Ranger 2, for almost full BAB, max bonus feats, and great skirmishing damage output. With a Human, you can get the following build up to level 6:
Scout 1 - Point Blank Shot, Precise Shot (H)
Ranger 1 - Track (B)
Scout 2 - Travel Devotion
Scout 3
Scout 4 - Swift Hunter (B)
Ranger 2 - Improved Skirmish, Rapid Shot (B)
You get Skirmish (+4d6/+3) with Improved Skirmish. You also get Trapfinding, Battle Fortitude +1, Uncanny Dodge, Fast Movement +10', Trackless Step, 2 Favored Enemies (I'd pick Magical Beasts and Undead), and Wild Empathy.
Attacks (conservative assumption of Str 14, Dex 18, composite longbow [+2]): +7/+7, for 1d8+3+4d6 each, or an average of 21.5 points, 25.5 against Magical Beasts. This doesn't include buffs, magic items etc.