Nedko's LV2 plug called 'lv2fil' (which is an LV2 of Fons' LADSPA 4 band parametric EQ is very good). I don't know about any good free multi-band comps, but I am told there plenty of good single band comps. Then of course you can use the LV2 Tom Slizilzilziziagy's Impulse Response reverb, which sounds amazing with the right IR files. I recommend the True M7 IRs.