OK, thanks. What are some (intelligent) mods that people like to do to these cars, with the intention of using them mostly on the street? Any easy, no-brainers like there are for most 911s?

If we're talkin' E36's I'll list what I've done and what I plan to do.

Rear Shock mount "Z3" upgrade
Wilwood big brake kit w/Euro E46 rotors up front from UUC
Turner rear rotors
Completely overhauled trailing arms with urethane bushings
Turner underdrive pulleys
Turner adjustable rear control arms
Turner sway bars
BMW MSport X brace
Tree House Racing front control arm bushings
Kosei K1 wheels / Bridgestone Potenza RE11's
Wheel stud kit from Turner (Out with those silly bolts)

Next in will be

Ground Control coilovers
Schrick cams
Turner software
Cold Air Intake
UUC RSC36 exhaust
Urethane subframe bushings
Turner subframe reinforcement kit
3.38 diff.

I admit I'm biased but e28 all the way.
http://forums.pelicanparts.com/off-topic-discussions/524062-ode-e28-m5.html