USB
[http://www.linux-usb.org/USB-guide/book1.html USB HOWTO]BR [http://www.linux-usb.org linux-USB]BR [http://linux-hotplug.sourceforge.net linux-hotplug.sourceforge.net]BR [http://qbik.ch/usb/devices list of devices]BR [http://usb.org usb.org]BR [http://usb-by-example.com book ]BR [http://lvr.com book USB Complete Second Edition]BR [http://lvr.com/usb.htm USB Central]BR [http://directory.google.com/Top/Computers/Software/Operating_Systems/Linux/Hardware_Support/USB/ links] on Google directoryBR ["3G USB"] modems and cards (i.e. http://wiki.debian.org/Usb_modem)
USB driver development
[http://marc.theaimsgroup.com/?l=linux-usb-devel linux-usb-devel mailing list]BR [http://usb.cs.tum.edu/usbdoc Programming Guide]BR [http://lwn.net/Articles/27352/ Linux "USB Gadget" API and Driver Framework] support for USB Gadgets ie for code running inside a USB "device"BR [http://ftdichip.com a USB chip]BR