In my case, trying to store blankets in a vehicle, the space saver bags (or whoopee cushion bags as I called them before) didn't work out so well. They eventually self-inflated, possibly because of becoming stiff in the cold.

I'll be trying the vacuum cleaner method on a regular plastic bag as soon as I find some heavy gauge ones around the right size. Also, the super-size ziploc bags sound like they'd be worth a go for some other items (thanks, massacre).