In my previous post the JTAG tools has been covered to an extent. Some more digging shows it would be really simple and cheap, yet still very effective.
An EETimes article explains this in depth. That gives us more confidence that the open source tools are really effective, almost as good as the commercial ones. The board mentioned as an example in the article can be found in a blog on lpclinux site. The lpclinux forum also has a detailed coverage of how to debug a LPC3250-Stick hardware using openocd.