http://www.miata.net/garage/
http://forum.miata.net/vb/
We did some mid-grade NAPA rotors. I was suggested the NAPA rotors by someone who basically races one of these. Actually what he does with the car is probably much harder on the car than what most race cars see.
For the pads we went with Potterfield R4S's
http://www.flyinmiata.com/index.php?deptid=4539&parentid=0&stocknumber=14-39100%20%201990-93
I can't speak too deeply into the R4S's, but they seem like a good option for the street. They've worked fine so far but we haven't beat on the car too much yet. I was going to do some mid-grade NAPA pads too, but I think these weren't much more expensive. I think the rotor price difference was much bigger. Also got a bottle of AET Super Blue, or whatever fluid you like, and bleed the brakes and clutch.
I ordered parts from these places so far with good success
http://www.flyinmiata.com/
http://www.good-win-racing.com/
Do ATE fluid in the diff and tranny. The tranny shifts like butter after it's warmed up now. http://www.flyinmiata.com/index.php?dept=27
You'll likely need to do the shifter boots.
http://www.flyinmiata.com/index.php?deptid=4531&parentid=0&stocknumber=08-46000
http://www.flyinmiata.com/index.php?deptid=4531&parentid=0&stocknumber=08-49000
The car was a non-LSD stock and we got a used stock LSD (newer type). It was expensive, but worth it. You can do that down the road.
Get a roll cage at some point too.