With the "Quick IK" add-on you can save time if you rig a lot with inverse kinematics.

The "usual" way to add IK to a rig is:

1) go to pose mode

2) select two bones

3) press Shift-I to add IK 

4) select the ik bone

5) change the chain length to the value you need

6) go to edit mode

7) select the controller bone

8) unparent the controller bone

9) go to pose mode again

-> use your rig

With this add-on you do these steps:

1) go to pose mode

2) select the controller bone, the IK bone and the chain-target bone

3) Press Shift-CTRL-I

-> use your rig