HDL simulators are software packages that simulate expressions written in one of the hardware description languages, such as VHDL, Verilog, SystemVerilog.
This page is intended to list current and historical HDL simulators, accelerators, emulators, etc.
Some commercial proprietary simulators (such as ModelSim) are available in student, or evaluation/demo editions.
These editions generally have many features disabled, arbitrary limits on simulation design size, but are sometimes offered free of charge.