You can save some money over the Battery Tender by going to Sears and buying their battery maintainer. I've used it successfully on my Optima battery for the last 2 winters (get's pretty cold, but dry, here). I drain the radiator and put in fresh A/F with corrosion inhibitor and a bottle of Redline Waterwetter. Of course, I have added Sta-Bil to the gasoline and ran it a bit to get it through the fuel system.
After all that, I let it sit for the winter. Seems to work OK for me.
I also use an Accumate charger/maintainer for my motorcycle and have found it to be outstanding. Here's a link for it:
http://www.hotrodssuperstore.com/acautcharand.html
Shop around for the Accumate as the price varies and it usually is about the same price as a Battery Tender, but can be found cheaper. These maintainers prevent sulfation in the battery which will short cells out if the battery isn't on a maintainer. Well worth the money and hassle come spring.
Paul