[SPF2245]

I think Ford has survived for a couple simple reasons. First, they bought Mazda, took their chassis, modern drivelines, and began selling re-bodied versions here. Next, Ford was good about securing large lines of credit before all went bad. Ford has done well to keep their line improving, they don't max out the life cycle of each product as often as GM does. Ford is more willing to take a product (recently) and keep making small changes to keep it's appeal. It appears they've learned from the mistakes they made with the Explorer and Taurus and have begun to make enough changes to appeal to new buyers.
Last, Ford isn't quite the giant GM is. GM is so large and exposed itself to so much risk (numerous brands, too many common products competing against eachother, huge credit firms, ect) to survive in the current economy.