Check out this little Secret Jolfather person picker webapp I made on my lunchbreak today. It's basically the closest you can get to "Santa" in my version of the Norse religion, but hey you can use it for whatever "secret" gift-giving practice you observe. Heck, use it for a secret Krampus office holiday event and send eachother horrible stuff if you want!
It has two options:
A direct swap in which everyone is matched directly to another person for a less-secret option, except for the last three people if the number of people is odd in which case they each have a person matched to them that they don't give directly back to.
A completely random swap in which each person gives to a person and gets from a completely different person to preserve complete secrecy of gift-giving.
Give them a shot if you have any need of an easy way to determine the gift giving for your next office party!