The best archer is an ELF! 19 Dexterity == +3 THAC0 with missiles!
For my archer I picked:
Short Bows: +++++
Halberd: +
Later I picked up Two-Handed Sword, Two-Handed Weapon Style and Quarterstaff.
But the important thing is the Short Bow. There are so many awesome short bows in SoA: Tungian Bow, Bow of Tacheron, and Gessen Bow, to name (and probably misspell) three.
-- Nifft