CharacterController.velocity
var velocity: Vector3;
Vector3 velocity;
velocity as Vector3
Description

The current relative velocity of the Character (see notes).

This allows you to track how fast the character is actually walking for example when he is stuck at a wall this value will be the zero vector.

Note: The velocity returned is simply the difference in distance for the current timestep before and after a call to CharacterController.Move or CharacterController.SimpleMove. The velocity is relative because it won't track movements to the transform that happen outside of the CharacterController (e.g. character parented under another moving Transform, such as a moving vehicle).
	function Update () {
		var controller : CharacterController = GetComponent(CharacterController);
		var horizontalVelocity : Vector3 = controller.velocity;
		horizontalVelocity = Vector3(controller.velocity.x, 0, controller.velocity.z);
		
		// The speed on the x-z plane ignoring any speed 
		var horizontalSpeed : float = horizontalVelocity.magnitude;
		// The speed from gravity or jumping
		var verticalSpeed : float = controller.velocity.y;
		// The overall speed
		var overallSpeed : float = controller.velocity.magnitude;
	}
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Update() {
        CharacterController controller = GetComponent<CharacterController>();
        Vector3 horizontalVelocity = controller.velocity;
        horizontalVelocity = new Vector3(controller.velocity.x, 0, controller.velocity.z);
        float horizontalSpeed = horizontalVelocity.magnitude;
        float verticalSpeed = controller.velocity.y;
        float overallSpeed = controller.velocity.magnitude;
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Update() as void:
		controller as CharacterController = GetComponent[of CharacterController]()
		horizontalVelocity as Vector3 = controller.velocity
		horizontalVelocity = Vector3(controller.velocity.x, 0, controller.velocity.z)
		horizontalSpeed as float = horizontalVelocity.magnitude
		verticalSpeed as float = controller.velocity.y
		overallSpeed as float = controller.velocity.magnitude