Work in progress » V-USB tutorial (software-only usb for mega & tiny) Arduino use the FTDI chip for usb communication (not anymore).
This chip is expensive and only surface mount. To save money and be able to make a PCB at home, i found a software-only implementation of USB for AVR (attiny, atmega): You don’t need the 2 LEDs (visual feedback for debugging / bootloader). Hardware Considerations - V-USB. Prototyping board: Many people ask for a prototyping board for V-USB.
There are a few available: Metaboard. This board is not available for sale, but it is very easy to build it yourself. Eagle3D: PCB’s 3D de Eagle con POV-Ray - tikitak-o-rama. Tutorial Eagle1. ESpice Web Site.
Linux.