Roy Bunce is raising funds for TRIFDEV a re-programmable FPGA I/O expander for Arduino on Kickstarter! FPGA based multiple I/O port shield for any bus. Ready to use, or develop your own control logic with free VHDL/Verilog software.
FTDI USB-to-Logic-Level-Serial cables. These are great to connect direct to a microcontroller's UART pins & versions available). They take care of all the USB stuff, and the UART just appears as a standard COM port to the PC!