THis is such a broad question-what are you really looking for? If it is chassis parts then Summit, Ultra Performance, and several others can supply poly bushings, sway bars, strut tower bars, coilovers, shocks, springs, etc. If you are looking for engine parts they can be had from the above and many other places. If it is JDM and "bling" look in the magazines and start calling around.
A word of advice: when you call these places ask a very good question about a specific item you intend to buy-LISTEN to the answer. Why, it will tell you something about the person's knowledge and how the business is run.
Happy Luding