I just threw together a quick hack for using your sdcard to store your library without rooting your glowworm or nook simple touch.
Many folks feel that the Nook Touch and Nook glowworm just don't have enough storage. I've repartitioned my unit so I have ~ 1 gig of onboard storage, but for folks with hundreds of books, that's actually not enough storage.
It turns out that you can very easily (three commands) tell your Nook device "hey, use this directory for storing files from BN, willya?" - and that directory can be your sdcard. (This approach will also work on the Tablet and Color devices; however, enhanced magazines probably won't work using this approach.)