I carry one USB charger and a simple extension cord in my bag. This Belkin product is a sure thing for my carry-on bag:
....stylish surge protector power strip looks like it would be right at home in any mobile Mac user's bag. It includes two powered USB ports for charging iPhones, iPods, and the like, as well as three AC outlets...
...The Belkin Mini Surge Protector is "coming soon" for $24.99.
The Belkin site mentions a "360-degree rotating plug with 4 locking positions". I assume the plug fully retracts.
This is a great boon when fighting for an airport outlet; most travelers will gladly relinquish an outlet in favor of the protector. My only change is that I'd like to see it ship with a 6 inch extension cord, I'll look for one that would fit.