The CVS tree and nightly build of Stripe Snoop now includes support for keyboard based magstripe readers, such as those made by Cherry Keyboard.
http://www.cherrycorp.com/english/advanced-line/keyboard-magnetic-stripe-card-read-series-g81-7000-8000.htm

While support is still primitive, you no longer need to build your own reader from parts to capture raw bitstreams. Futhermore, the cost of a Cherry keyboard is about 1/2 of what it costs to get the parts! A Force Mode has also been added to parse damaged and nonstandard cards.

Stripe Snoop builds for Linux and Windows, with BSD/Mac support in the near future.