It depends on how long I've got left.
I'd first try to make my peace with those I may have hurt during my lifetime. I'd talk to my rabbi, and try to set my spiritual affairs in order, as it were.
I'd set my financial affairs in order as well.
I'd speak with all my friends and sisters, by phone if not in person. This includes a few old childhood friends that I've lost touch with over the years. I probably wouldn't tell them that I was about to die, though, except for my very closest friends.
I'd spend some time with my parents.
If I had children, I'd do something special with each of them.
Depending on how long I had left, I'd take a trip around the world with my husband and visit all the places I always meant to see that I hadn't yet, and revisit all the places I've been that I always wanted to get back to.
On my last night on earth (borrowing what docetboy said), I would enjoy a fabulous evening with my husband, pulling out all the stops. I would want to die asleep in his arms.
God, this thread is morbid