I have a 1994 Dodge Intrepid in the garage whose battery goes dead if not driven after a couple of months. If I buy a disconnect or (cut-off) switch, http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2446028932 can I expect a new battery to keep a full charge throughout the winter?

Probably a better solution would be a battery 'tender' type charger. This will prevent the battery from coating the plates. See http://www.batterytender.com/ for one example.

My opinion.
I do like the Battery Tender. However, shop for price. Bought one for far less than the factory site sells it for.