If you are recording with Audacity or another software which supports VST plug-ins, Kjaerhus Audio offers a free, high quality set of VST effects. The Classic Series effects all faithfully emulate hardware effects boxes, and include a compressor, EQ, master limiter, and reverb, among others.

One of the cool things about these plug-ins is they have some useful presets to get you started, but if you want to go further and learn what the different knobs do, you will have a great foundation of knowledge to operate hardware effects units of the same effect type.