I'm somewhat obsessed with Project Oberon. This description of the project explains why:
"Project Oberon is a design for a complete desktop computer system from scratch. Its simplicity and clarity enables a single person to know and implement the entire system, while still providing enough power to make it useful and usable in a production environment. "
I grew up using computers that I could understand, all the way down to the metal. These computers came with block-diagrams of the hardware (if not literal schematics). "Modern" computers are considered too complex to provide users with this kind of information, but Project Oberon proclaims that they don't have to be that way.
In it's current form Project Oberon goes one step further than the 8-bit micros I cut my teeth on, providing even lower level access to the computer's design. This is only possible due to the advent and availability of FPGA hardware at consumer-level prices. You could part-together a set of Project Oberon hardware today for less than the cost of a Commodore VIC=20 back in the '80's (and that's in unadjusted dollars).
I still haven't pulled the trigger on the hardware myself, but I get closer every day. I've read all the documentation at least once, but I want to get a little more proficient with the emulator before plunking down cash for the hardware. I'm also still aiming to build-out a laptop version of the computer, and there's a few struggles to overcome due to the VGA video and PS/2 I/O of the board.