one of the less advertised features of the nexus 7 is the fact it supports usb otg, which allows you to plug in certain usb peripherals.
the devices i've tried are mouse and keyboard, these just plug in after buying a cable
and they just work; even a power guzzling gaming mouse worked fine.
from what i've heard it's even possible to use a small usb hub or an external flash drive [that may require rooting], but i havn't tested these myself. it should also be noted that not all android devices support usb otg; for instance a usb mouse does not work with a nexus s.
also i knitted a case. just wanted to show off. i'm not going to pretend like i'm good enough to explain how to knit, but if you are going to knit one the dimensions i used are 42 stitches on 4mm needles and 4mm wool
. 1 ball was *just* enough to fully cover the tablet but i would recommend 2 for a properly finished case.