To save money and market to many different individuals, a lot of automobile companies have ‘platform sharing’. For example, the Mazda 3, Volvo S40, and Ford Focus (all owned or partially owned by Ford Motor Company) all share the same platform. Also, you have the Mazda Tribute, Ford Escape, and Mercury Mariner. I already know that Wiki says this.
What are other examples of platform sharing?
Doesn’t that wiki link pretty much cover things? It seems to do so for most brands sold in the US. It’s mostly up-to-date for Ford, GM, and Chrysler.
The Toyota Camry, Avalon, Lexus ES330, TX330, Highlander and Sienna are all on the same platform, probably one of the most extensive.
Make that RX
It is not totally up to date, and I was also wondering about cars throughout, not just in the US.
I’ll just throw out a couple of examples - you’re asking for more research if you want an exhaustive list:
Honda Civic, CRV, Element & Acura RSX
Honda Accord, Odyssey, Pilot, Ridgeline & Acura MDX
Yugo & Porsche 911 & Hummer H1 (little known fact)
Hot damn! And I almost spent all of that money on that Porsche, knew the Yugo for $13,000 was a great deal.
My Pontiac Sunfire shared a platform (the GM J platform) with the Chevrolet Cavalier. The new Dodge Chargers, Magnums, and Chrysler 300s share the Chrysler LX platform, and all three cars are built just around the corner from here in Brampton.
Is this a whoosh or a DRI? 
I am for sure going to have to see a very good cite for a 911 and a Hummer sharing a platform.
It is possible that Porsche Cars AG did some engineering work for AM General during the development of the H1, this does not mean that they share a platform. Porsche and Lotus both do engineering consulting for other car companies. Porsche for example did some cylinder head flow work on the Volvo 960 engine back in the early 90’s.
Getting back to the OP all of the following share a platform
Volvo
S80
V70
S60
XC70
XC90
The platform is now also being used on
Ford
500
Freestyle
Mercury
Montego
What ever the hell they call their version of the Freestyle
One thing about the OP list on the S40. The S40/V50 only shares a platform with the Mazda 3 and the Focus C-Max which is a European only Focus. The Focus that is for sale in the US is a different platform.
GM Epsilon Platform:
SAAB 9-3
Chevrolet Malibu
Pontiac G6
Cadillac BLS
Opel Vectre/Signum
GM Delta:
Saturn ION
Chevy Cobalt
Chevy HHR
Pontiac G5
I believe the Dodge/Plymouth Neon (is that still made?) shares a platform with the Chrylser PT Cruiser.
A couple years ago, Mercedes redesigned its roadster. The old one lives on, in a new skin, as the Chrysler Crossfire.
The Pontiac Vibe and the Toyota Matrix are nearly identical.
That itsy Smart car seems to share a platform with the world’s biggest-selling car, the Cozy Coupe. I could be wrong about that one.
Nissan 350Z, Infiniti G35, and Infiniti FX SUV
I knew that because I have a 350Z, but lo and behold, Wikipedia has a page on shared platforms. All you need to know about BMW, Chrysler, Ford, GM, Mazda, Nissan, and VW platforms.
The Volkswage Touareg and Porsche Cayenne share a platform, even though both companies are independent of each other.
And the new Audi, which is part of VW. Porsche and VW aren’t in the same company family, but they’ve had a business relationship for decades.
More than that, they’re essentially the same car with different badges. They’re built on the Corolla platform which is used for several other cars.
Nope, it’s now the Caliber, and will be the basis for the new Avenger. I don’t know if the PT Cruiser will follow to the new platform.
That would be a whoosh.
That link is in the OP.
D’oh!
I found the link on my own, and then looked through the thread for other links, but it was already gray instead of blue.
Is there a Subaru/Volvo combo?
Most Peugeot and Citroen cars share the same platform . There was a news feature in the paper the other day saying that Fiat are to revive the classic “500” in conjunction with Ford. The Ford version will replace the “KA”
Yeah, and the smallest car in their ranges, the 107/C1 is also shared with Toyota as the Aygo.
There’s also a notable difference between platform sharing as in the Volkswagen group and badge engineering where there’s barely any difference between even the body work.
The VW Group shares many platforms across many of its companies. The VW Golf, Skoda Octavia and the Seat Leon have a common platform. The VW Passat shares its platform with the Skoda Superb. The VW Polo and Seat Ibiza share a common platform. I think the Audi A3 also shares the Golf platform, but I can’t be certain - Audi likes to keep its identity separate from VW.