PLMS cables are GREAT.
ECUTalk cables are GREAT @ $85AUD shipped !
other cables and DIY jobs are (in my opinion) not worth the time. I have done a DIY cable before, it was OK, but would encounter problems every now and again with it, right when i needed it to just work and not mess up.
I have an ECUTalk cable that i use with nistune (and with general diagnostics) and its been totally flawless.
PLMS cables are also very well designed, a little less compact but includes diagnostic lights which can be a good quick way to detect issues (lack of data/communication, no power etc).
I highly recommend getting a commercial cable and spending the money on a decent one that is reliable. There are a few DIY designs floating about (google will help, i have no immediate links ready to go).