Don't think so

To the best of my knowledge, there's no way to do this presently. Unless you have a model with a HDD and are willing to remove the HDD to be put in your computer. Then with the help of a special program, you can read the drive and put things on it. This will void your warranty and you could break something if you don't know what you're doing though.

Otherwise, you'll just have to wait for the first full blown modchip for the Xbox 360. No idea when it will be out... Could be days, could be months, could even be years. It will likely come out at some point, and once people are able to run unsigned code on the console, you have a good chance at being able to use flash drives.