When the cue ball is touching two or more object balls, and at least one is a 'ball on', so long as the player plays away from at least one 'ball on', the player may play into any of the other touching balls without penalty. 

This also applies to an open table, where both sets of coloured object balls are on. For example, if the cue ball is touching a red and the 8-Ball, the player may play away from the red and into the 8-Ball.