Here are a few of my favorite links.

[MicroNut]

Here are many of my favorite links. Do you have any to share? The more the merrier. Knowledge is power!

Electronic/Computer Forums
Savage Chats .. of course!
Parallax Forums All things propeller, and probably the only place.
Sinclair ZX World All things Sinclair. Mostly about my first computer the ZX81!

FPGA
Open Cores A repository of open source FPGA IPs. Sometimes works, sometimes don't
Nand Land Videos and tutorials on VHDL and Verilog languages. He has good examples, has the FPGA Go Board and a book based on it.
fpga 4 fun Has great examples. Serial ports, oscilloscope, games and more
8 Bit Workshop Java Web simulator for FPGA verilog, old 8 bit computer and game consoles. There are links to ebooks that help in using the web simulator.
Project F Verilog projects and a RISC cpu
FPGAcademy If you have an Altera/Intel DE board this is a good starting point for setting up projects and the Quartus IDE

Z80
Z80 Every Z80 documentation you can find!
Baltazar Studios A project site with a Z80/Arduino, Die level reversed engineered Z80 FPGA and a Die level Z80 simulator in java
Ken Stirriff's Blog A blog going into the netlist of the Z80 and other CPUs

Simulators
Logisim Evolution A java based Logic simulator that can generate VHDL/Verilog files for FPGAs
Digital Another java based logic simulator similar to Logisim
Simulide a free simulator that does logic, Z80. Arduino, ESP, TTL and other components