Depends on how big the office is. Smaller offices, it's the office manager, who usually doubles as the HR person. Slightly bigger offices, the office manager can delegate to the Admin or the office secretary. once you start getting into larger offices, each dept tends to do their own. I worked in an office of 300-400 women and we had an Employee Association, who spent the entire year doing raffles and small fund raisers, to raise enough money to plan the Christmas Party for the employees. The company management team had nothing to do with the holiday parties. So it just depends.
I agree...try to do most of them personally (maybe attach a small treat), if you cannot at least snail mail. Emails get filtered to trash or just gets deleted. Remember...you are not the only offer they will get!
I would drop off a small plate of samples and then after you are able to speak to someone mail a colorful postcard or note to keep you in their minds! This way you can mail it direcly to the correct person. This is especially for the larger companies.
Tracy
Our receptionist is now stuck with the job of party planning!
In my secretary days, I remember just that feeling.....being "stuck" doing that crap!
First year that I got promoted to the manager's secretary and one of the ladies asked me when I was going to start collecting money for the boss's christmas gift. I said, "why would I do that?" She said, "Because the other secretary always did it!" I said, "Then you better call HER and find out when SHE is going to collect money. I dont' like christmas shopping for my family ... I'll be damned if I get stuck doing it for people at work."
And so she formed a committee to buy a gift for the boss! 
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