As you move models in a unit, they can turn by any amount without any penalty to the distance they are able to cover. Models are turned to face their targets in the shooting phase so don't worry about which way they are pointing at the end of their movement phase (although dramatically facing off against their foes is traditional).
Turning and Facing
Source: 3rd-A-Palooza (3.5) Rulebook v1.4, p. 4