At Silicon Dream 2013 Chris Smith was showing off his hand built ZX Spectrum ULA. The ULA is the heart of the Spectrum and Chris has reverse engineered the custom chip and written a book about it. There was a massive amount of painstaking work that went into the original design and Chris explains about the why he started work on the project.
Also in this video is a ZX Spectrum that connects to the internet via Spectranet an Ethernet interface for the computer. This Spectrum was connected up to Twitter and Dylan Smith explains what you can do with it and why build it.