Check out this low cost .NET Micro Framework board from GHI Electronics -

The GHI web site also contains a video of the board being used to play a .MP3 file from a USB stick - pretty cool!

 

The board is listed at $99, and has the following hardware and software features.

    Software:
  • Micro Framework 2.5 and 3.0
  • USB Host (MS, HID, Printer and more)
  • FAT File System
  • Peripherals (SPI, PWM...etc.)
    Hardware:
  • 72Mhz ARM7 Processor
  • USB Host/Device
  • Plenty of Digital I/O
  • Interrupt Inputs
  • SPI (8/16 bit)
  • I2C
  • 4 UART
  • 2 CAN Channels
  • 4 10-bit Analog Inputs
  • 10-bit Analog Output
  • 4-bit SD Memory Interface (uSD connector)
  • PWM
  • Low Power and Hibernate Modes
  • -40 to +85 Operational
  • Lead Free

[UPDATE] GHI have a projects page that includes sample code, and some videos showing the code running - here's a link to the page.

- Mike