maybe not yet directly, if that is what you meant.
But in-directly, meaning network or via shared over your network, Yes
Although it is not through any UI of the iPhone OS, but through 3rd party developer apps, such as;
The Android group just had a lot of luck hacking USB to work on that platform for a number of devices, so yah like AbblePC said it shouldn't be too hard.
I know there is a USB over IP implementation in the wild as well.