If you have a 3.3V FTDI cable, turning it into a Propeller programming cable is rather easy. A modified cable is cheaper than a propplug, too!

You can also build a serial-only cable using the FTDI design, it only requires a DB-9, a couple transistors & passives:

First get yourself a FTDI cable, make sure its the 3.3V version!

Use tweezers to lift up the black connector tabs

Then pull out the wires

Repeat for all 6 wires

Now reassemble the cable, starting with the black wire

The cables should be in the order: Black, Green, Orange, Yellow.

Finally, a little electrical tape wrapped around the unused wires (Red and Brown) and onto the cable keeps it nice & neat, without risk of the Red wire shorting out to the others. When plugging in, make sure the black wire goes to VSS

Start up the Propeller tool and go to Preferences... Then under the Operation tab, select RTS as the Reset Signal.

Power up the YBox2 (or your favorite Propeller project) and plug in the cable so that the black wire goes to VSS.

Now start up the Propeller software and select Identify Hardware

You should get the following notice, indicating everything is good to go: