Your husband will not pay any tax on the gift. The person who receives the gift does not pay any tax.
Your father in law will file gift tax return Form 709 to document the gift. A person can give any number of gifts of less than $12,000 to any number of persons. All gifts of more than annual exclusion amount ($12000 for 2007 & 2008) must be reported by the donor. There is a lifetime exclusion of $1 million. A person making a gift in excess of $12K must include the gift in the lifetime exclusion and file Form 709 to document the gift. He will not pay any tax till he exceeds lifetime exclusion limit. This will also be counted in his estate exclusion limit.
If your father-in-law is married, both he and his spouse can separately give up to $12,000 to the same person in 2007 without making a taxable gift. Since it is already December, if your father-in-law makes gifts in 2007 and 2008, he can use exclusion limit for both the years. But he will file Form 709 for both the years if amounts exceeds the exclusion limit.
Publication 950-- Introduction to Estate and Gift Taxes.
Internal Revenue Service