which companies are the main sponsors for the cup series?
Chevrolet,  Ford and  Toyota
2006 NASCAR Nextel Cup Series
Tony Stewart, driver of the No. 20 Chevrolet for Joe Gibbs Racing, was the defending series champion, but lost out in defending his championship this year, having finished outside of the top 10 in the points standings after the Chevy Rock and Roll 400. 
what is 2006 bank of america 500? 31st stock car race of the 2006 NASCAR Nextel Cup Series what is the qualification to enter this race? UNANSWERABLE
wiki:596404
2006 NASCAR Nextel Cup Series [SEP] Introduction
He did, however, claim a $1 million (US) bonus as the best finisher outside the Chase for the Nextel Cup drivers, winning three of the ten Chase races. By the end of the season Chevrolet had captured 23 victories, and 270 points to win the NASCAR Manufacturers' Championship over Ford. The 2006 season was the first for Ford's all-new Fusion, which replaced the Taurus both in NASCAR and in showrooms. Also, a new version of the Chevrolet Monte Carlo, called the Monte Carlo Super Sport (SS for short) debuted on the circuit. Additionally, 2006 was the first Cup Series season since 1979 without Rusty Wallace and 1974 without Ricky Rudd, although Rudd made one appearance in relief and would return for one final year in 2007 before retiring.