Directly from their site:

Your membership entitles you to:

* Exciting, colorful monthly magazine
* Discounts on parts and supplies
* Free classified ads
* Video services
* Distinctive club decals
* Driving Events
o Driving Schools at Internationally renowned race tracks
o Autocrosses
o Rallies
o Tours
o Gymkhanas
* Technical tips and information
* Camaraderie
* Outstanding National Events - Oktoberfest and TechFest


You may be eligible to receive an allowance based on the purchase or lease of a new or Certified Pre-Owned BMW through an authorized U.S. BMW center.

* A membership of one year (365 days) or more immediately preceding the purchase date of the vehicle is required to take advantage of this program.
* A member in good standing cannot have any lapse in membership during that 365-day period.

Terms and Conditions:

1. Only those vehicles purchased from authorized BMW centers in the U.S. qualify for the purchase allowance.
2. The BMW Car Club Allowance is non-transferable and can only be redeemed by a car club member. Sales documents and vehicle title must be in the member's name. If a member co-signs for a vehicle with a non-car club member, both must reside in the same household. If a member co-signs for a vehicle with another car club member, both must reside in the same household, but, there can only be one rebate submission.
3. This program is not available in conjunction with other special purchase programs offered by BMW of North America, LLC, including but not limited to the Vendor Program or any other certificate offer.
4. Vehicles purchased or leased through a 3rd party (i.e. brokers, lease companies, etc.) do not qualify.
5. BMW allows one rebate per calendar year per member and only one member can apply for a rebate if there is joint or multiple ownership of the vehicle.
6. For certified pre-owned vehicles, rebates will be paid once per vehicle per customer.
7. BMW is not responsible for late, lost or misdirected applications.

Eligible Vehicles:
New passenger cars (including European Delivery), new SAVs and Certified Pre-Owned vehicles.

I don't know about car discounts but I get 10% on parts.

Its a great way to meet people with common interests (like this forum) and our club events are usally heald at cool places like dealerships, body shops that fix exotics, etc...not to mention the occasional driver schools and track events that many members participate in. My father has been a member of the BMWCCA since 1978 and I have been an associate member since 1986 and full member since 1996...well worth it.