Can someone please tell me how long the NASCAR season is from start to finish?

May be...

The 2008 season began with the Bud shootout on February 9th, and it ends on November 16th at Homestead.
So about 9 months. 36 points races.

It is 36 races plus 2 non point races the shootout at the beginning before Daytona and the all star race at Charlotte starts in February and ends in Nov at Homestead

NASCAR has something going on every month of the year (Cup level). In January, they spend 2 weeks testing in Daytona.
In February, they go down for Speedweeks (back to Daytona that is). They practice and run the Shoot-out on the first Saturday in February. This is a non-points event that drivers participate in only if they've won a pole the previous year (or in on a provisional). The next day (Sunday) is pole day/qualifying. They then run more practice through out the week. That Thursday they run the Duels. These are 2 qualifying heats that set the field for the 500. Then, more practice. On Sunday (the 2nd Sunday in February), they run the 500. February is typically rounded out with the California race.
March brings Las Vegas, Atlanta, Bristol and an off week. This year Martinsville was raced in March, but this is not the norm (it fell on the 31st).
April usually brings Martinsville, Texas, Pheonix, and Talladega.
May is Richmond, Darlington, the All-Star Race (non-points) and the Coke 600 at Lowes.
June brings Dover, Pocono, Michigan, Infineon and New Hampshire.
July brings the Firecracker/Pepsi/Coke 400 (the Daytona 4th of July race- it has had multiple names), Chicagoland and the Brickyard. Plus an off-weekend.
August is full of Pocono, Watkins Glen, Michigan, and Bristol.
September has California, Richmond, Dover, Kansas and New Hampshire.
October has Talladega, Lowe's, Martinsville, and Atlanta.
November ends the regular season with Texas, Pheonix and Homestead. Homestead always falls on the Sunday before Thanksgiving.
December hosts the banquets. The Cup banquet is held on the 1st Friday of December.

So, to answer your question, the NASCAR season is year long :)
The point paying race season is 36 races in length, going from the 2nd Sunday in February until the 3rd Sunday in November. Plus, add the 2 extra events (one before the season begins!) and testing and you get a full year worth of NASCAR!!!!!

11 month