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 directory[[BR]]
 ["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]]