I have an Alesis IO Dock, its a great piece of kit, not only do you get the Audio and MIDI IO for your iPad (Vintage, and iPad 2), but it charges the iPad at the same time.
While it has a USB B-Type port for hooking up your computer, it doesnt allow for A-Type connection - for instance if you wanted to connect a USB controller directly.
Cunning DIY hacker Untergeek has come up with a guide on just how to make this possible - you just need a Dremel tool, an active USB hub, a couple of cables, some glue and a steady hand. He explains all of this in his video - the full guide is listed below.
Thanks to the excellent Discchord for spotting this one.