During the holidays it is always nice to tip the mail man, your hair dresser, the doorman, etc. Holiday Tipping is about Holiday Thanking!
I know this year is tougher then usual but don't forget to do something -any token is appreciated. If you plan to do a monetary tip - do only 10% of service instead of 20%. Maybe make cookies or fudge with a nice note instead.
I plan to make some candy for my mailman - he has been so nice to me this year.
Emily Post has some good etiquette advice about holiday tipping. Check it out. She even lists some recommendations in a table.