It isn't really that hard and even if you find a site it will take practice to become proficient at it.
Just work from the lowest stack to the highest. Count out the chips of each player who is all in, take the lowest stack's amount and place this amount from each player's stack into the main pot. Then repeat this process, creating subsequent pots until you are left with only one player and return the remaining portion of his stack to him. Be sure that you remember who is eligible for which pot. It is helpful to remind the players of this BEFORE the remaining cards are delt.