I just bought a lightsnake analog to USB converter - this thing is completely bad-ass!
Take a look at it RIGHT HERE.
I got mine at Target for $40 - this is a great device to record straight from your guitar (or any other live instrument) directly into a USB port.
So far it integrates almost flawlessly with several apps - I've run into very very slight latency issues but with a few minor adjustments you can barely even notice the latency at all.
I know that the "how do I?" has come up a few times and so far this seems to be a terrific and inexpensive solution.
I highly recommend this device.