Looking at some of the embedded Linux units, eg the GuruPlug that I have sat on my desk and have never got around to playing with, a lot of them mention JTAG.

It's been a long time since I played with this type of kit and it seems that things have moved on from the days of UV lamps for wiping EPROMs, but I can't find anything useful but short about what JTAG is/does and whether JTAG is just JTAG or it's one of the standards that require you to pick the right JTAG programming kit to match the hardware.

Anyone around these parts able to give me a quick intro, or point me to one? At this point I really just want to know whether it's even something I need to know about!

The High Level guide here: http://www.xjtag.com/support-jtag/jtag-introduction.php

.. looks great but is still a little to low level for me at this stage!