It's called a fuel line disconnect tool and it costs under 5 bucks at napa or autozone.
Here are some photos of some sets I found through google:
http://www.mytoolstore.com/astro/asthan13.html
Essentially the tool goes between the connection of the two hoses and releases them. It is a high pressure connection, that's why it's such a PITA to disconnect.
Good luck,
-bear