Similar to, or, yet another attempt at building a registry of open source VHDL cores, simulation models and implementation constraints.

NEORV32: 32-bit RISC-V soft-core CPU and microcontroller-like SoC in VHDL @umarcor
VHDL/Verilog Cryptography cores incl. co-simulation with openSSL through GHDLs VHPIdirect @tmeissner
Microwatt and GHDL - An Open Hardware CPU written in VHDL, Synthesized with Open Source Tools @umarcor