budget digital interconnect

any recommendations for a cheapo digital cable for a second, budget system? (for that matter, is the difference between a digital coax cable and a RCA just the shielding?)
Canare makes a decent budget 75 ohm cable at well under $50 and it's as low as I would go--that or Apogee Wyde Eye. Make sure you get a 1.5m length. If you can go up a smidge to about $150, the Atlas Compass is a good one, or a VH Audio cryo Pulsar.
thanks all - lots of great ideas and helpful info.
I meant really cheap - and Loomis' suggestions ($10) are what I was hoping to hear of.
Second Hifixpert's suggestion of the Bluejeanscable digital cables. Great build quality and sound with exceptional service. Their Belden 1694A-based cable is $16 for a 3' length.