UUC offers a very comprehensive short shift kit. In the end Ron Stygar seems to have developed a kit that is much cheaper and just as effective. If you drive any BMW other then the M Roadster it is probably worth the money to upgrade to a short shift kit. But I feel the factory M Roadster/Coupe has a short enough shift and isn't really necessary (though the e36 M3 does need a shift kit).
Clutch stops have been discussed ad nauseum on the message board, so I'll keep this short and sweet. I bought the UUC Clutch Stop which was the only available clutch stop at the time. Ron Stygar has since developed a gorgeous stealth clutch stopped manufactured in Delrin. It is the clutch stop I would get. If you have any problems with side-to-side play in your clutch you shouldn't purchase a bigger clutch stop... ask Ron about his fix which properly replaces the spongy factory bushing with high-tech Delrin bushings.
Ever notice how if you try to shift (especially in a corner) that the gear isn't always where it should be? The factory BMW tranny mounts are designed for comfort instead of performance. They have an hourglass shape that easily deflects. After having this strange phenomenon happen to me at the top of the Corkscrew at Laguna Seca and the top of the Cyclone at Thunderhill I decided to do something about it. I installed a set of the Tranny Mount Enforcers from UUC. The product works as advertised in that it has greatly reduced the deflection inherent in the stock mounts and it doesn't raise the interior noise level like some of the products out there that replace the entire transmission brace.