I guess the title says it all. I played some Call of Duty: World at War with a friend, co-op online when it came out. It was fun, but as far as I could tell we couldn't save our progress. Recently we both picked up Resistance 2 thinking it had a campaign we could both play online. That game doesn't do the campaign, just individual levels I think. So what games are out there that we can run through together online and save our progress so we can play bits at a time?
First game that comes to mind is Resident Evil 5. Not sure if my friend has any interest in that one or not, though.