USB-OPTO-RLY88 - 8 optically isolated inputs, 8 relays

Powered & Controlled from the USB bus.

Relays - 8 
Isolated Inputs - 8
Power - Powered from standard USB bus
Control interface - USB 
Input Voltage - 4.5v DC to 27v DC
Relay current - Up to 1Amp @30vdc or 60vac. 500mA@110vac. 250mA@250vac 
Connections - Screw Terminals for N/O, N/C, Common contacts and +/- Inputs.

Full USB-OPTO-RLY88 Documentation 

Examples:
Linux
Linux GCC - A command line tool that will set the relays and display input states
Linux with Mono and Xbuild (C#) - Simple example of switching the relays and displaying inputs

Mac
Xcode - Simple example of switching the relays and displaying inputs

Microsoft Windows
Visual C# Express - Simple example of switching the relays and displaying inputs
Visual Basic Express - Simple example of switching the relays and displaying inputs