OK. Bottom feeding rack material and assuming you actually need this stuff:
For inexpensive, but usable EQ, you might look for a pair of DBX 242s. Probably the best units from the Project 1 series and designed by Robert Orban if I remember correctly. Used, they go for @$120 each or so (they are discontinued so used is all there is). Moddable. Very nice cheap EQs. An alternate would be the discontinued Symetrix SX201. They run about $65 each on e-bay and are half rack units. Both use wall wart power supplies so make sure you get the right power supply with them or you will need to track one down (easily available but a pain).
For compression, the RNC is a great usable compressor for cheap. IMHO there isn't anything close for near the same money. It is a stereo unit, but not a dual mono unit. I also like
the Aphex Compellor if you want very, very transparent compression (not the box to use if you want compression as an effect). Other usable compressors for cheap are the Symetrix SX206 (multi-dynamics processor) and SX208 (stereo compressor). Discontinued but you can find them for @60-70 each on e-bay. I think these are pretty usable and musical boxes. Built like tanks. The Symetrix 501 compressor is also very usable. I have one that I use primarily for bass. About $125 used. Get the one with the toggle power switch.
For reverb and some other effects, the Kurzweil Rumour/Mangler are really, really good. I think the Rumour is easily the best reverb box for under $500. The converters in these boxes are surprisingly good too and can be used on their own. I have a Rumour and a Lexicon MPX 500 and use the Rumour most of the time unless I want an identifiable Lexicon sound.
Other intersting, cheap and usable boxes for effects include the Effectron II and III (for lo-fi digital delay) and the Peavey AMR Tube Sweetener to add some tube roundness to your signal (same heritage as the Peavey VMP-2 tube pre and VC/L-2 compressor - which is to say they are not your typical Peavey boxes -- much better made). The Peavey Valverb is also nice if you want some real tube reverb although it is not the quietest box as it was designed for live guitar use.
As always YMMV, but I have found these all to be very usable and they are relatively inexpensive.