Sponsored by an energy drink, appropriately enough, that archetypal, Leave It to Beaver-esque kids event, the soapbox derby, gets an adult twist at the Red Bull Soapbox Race. The cars of the 36 participating teams will be judged not just on speed, but on creativity and showmanship; if youve ever wanted to see a wheeled vehicle in the shape of a skull, a taco, or a Swiss army knife, heres your chance. The rules are straightforward: only human (and gravity) power allowed, no prefab cars, nothing over 6 wide, 20 long, or 7 talland no drivers under 18. Fremont Ave. (of course), between N. 41st and N. 36th Sts. Races start at 1 p.m., pits open at 11 a.m.