I agree with all those that suggested a grab bag/Secret Santa. We did a really fun one at my workplace last year that was a 5-day thing.
http://www.essortment.com/office-chr...nta-45355.html
It involves a questionnaire that each participant (you must sign up to participate) completes. Then their Secret Santa uses those responses to shop. First day is a free gift, second day $1 or less, third day was something they could use in the workplace, fourth day was something they could wear & final day was a personal gift. We set a total cost for the whole week of something like $15. Then, on the final day you could use what you learned about your co-worker to make some small-ish item like a make-up bag, pot holder, mug rugs, baby bib, etc.
Otherwise, the most I would do is to make mini stockings for each co-worker & put a few candies in each with a little note. I had a boss do that for us one year & I kept it to this day. It was really sweet to find this tiny fabric stocking on my desk when I came into work one day near the holidays.
