If you like to do your own bike maintainance and you want to keep your bike in top shape then from time to time you'll need to repack your wheel, hub, and headset bearings (unless they're sealed units), and to do that right you need some quality bike-specific grease like Finish Line's Teflon Grease.
This grease wears very well and does an excellent job of preventing corrosion and distortion of you bearings, even in the worst wet-weather and winter conditions. It's also extremely slick and greatly aids the performance of your bike's moving parts. At just $12 for a tube that will last you a while it's well worth the price. If you've got a rainy day with nothing to do maybe it's time for a bit of a bike overhaul - don't forget to pick up your Finish Line Teflon Grease before you start taking things apart.