When: 1888. Why: First "point and shoot" camera for non-professional photographers.
Also, this is the first camera by George Eastman, inventor of transparent photographic film. "Point and shoot" relates to one of the best known slogans in photographic industry: "You press the button - we do the rest". And that was true. Photography enthusiasts had to press button (100 times for 100 photos on the roll) and send camera back to "The Eastman Dry Plate and Film Company" which developed film, printed photos, reloaded camera, and sent it back to customer for $10. In 1888 this pre-loaded camera was offered for $25 (kind of a high price back then), and currently it can go for up to $5000. Check out the Eastman's patent for this camera.
UPD: As it appears, George Eastman was not the "first" inventor of transparent film, nevertheless he popularized it, starting a huge change in the photography history.
When: 1947 Why: First SLR with instant return mirror.
This is the Hungarian camera, designed and built in Budapest, by Jeno Dulovits. Unfortunately focusing and viewing were separate operations but "Asahiflex IIb" came out on 7 years fixing this inconvenience. Since there were only about 800 Duflex cameras manufactured, the Asahiflex IIb one is usually called the first mass-produced SLR with instant return mirror. Currently, this feature is "a must" in any modern SLRs.
Duflex was also the first SLR to implement metal sheet focal plane shutter. Novacon site is a great source of information about this camera.
When: 1929 Why: First rollfilm TLR (Twin-Lens-Reflex).
Also it's a first medium format Franke & Heidecke camera. Franke & Heidecke manufactured a couple of stereo TLR camera models before (Rolleidoscop), but again, those were stereo cameras, not exactly suitable for the regular job. Rolleiflex Original was an instant success, and became a parent of many more TLR models which are still produced. You can find detailed specs of this camera on the Rollei Club web-site.
Ermanox is mostly known for its Ernostar 100/2 and 85/1.8 lenses. Even now, 100/2 lenses are considered as extremely fast, but in 1924 they were revolutionary, allowing previously impossible low light photography without a flash. A couple of years later, Ernemann introduced Ermanox Reflex which is highly sought by collectors and fetching really high prices.
Zeiss Ikon continued production of Ermanox after merger with Ernemann. Later, Ermanox lenses became a base for Contax Sonnar fast lenses line.
When: 1963 Why: First TTL (through-the-lens exposure meter) SLR camera.
Though TTL was already on the market with non-SLR "Mec 16 SB" camera, Topcon came in with several nice features: SLR (of course), interchangeable lens, interchangeable viewfinders, motor drive option. Currently, TTL is very important for SLR cameras mostly because of different interchangeable lens and different lens filters.
Welcome to the modern world of autofocus. Konishiroku used a Visitronic AF system designed and manufactured by Honeywell. It was expensive camera with passive system (comparing to active infrared ones) and only two photocells, nevertheless it started a significant change in the cameras world. Today it's almost impossible to find a new camera/lens without autofocus feature.
Also, this camera was almost fully automatic. The only manual thing you'd need to do is rewind.
When: 1917 Why: No.3A Autographic Kodak Special was the first coupled rangefinder camera ever
While rangefinders (or "telemeters") were introduced in the beginning of 1900s, they were used as optional accessories and were not linked to the taking lens (non-coupled). Their measured values had to be transmitted to the focusing scale manually.
Coupled rangefinder was "automatic" if I can say so. "Kodak Range Finder" (you can see it as a rectangular box under the lens) had three vertical mirrors in place (camera had to be held horizontally), and image in the middle one was shifting up or down when focusing was changed.
The whole new era started with this camera introduction. Rangefinders became an industry standard until SLR cameras didn't push rangefinders out.
When: 1949 Why: this is the first SLR (Single-Lens Reflex) camera to use pentaprism. Also it is the first camera to use 42mm screw lens mount (M42)
Pentaprism allowed non-reversed direct viewing from behind the camera, opposing to older SLRs top-view and reversed image. Pentaprism (or cheaper version: pentamirror) became an industry standard for modern SLR cameras. M42 mount, which was introduced for this camera, became an industry standard for 35mm cameras too. Later, M42 was called as "Pentax thread mount", "Praktica mount" and "Universal Screw mount" and was used on lots of SLR cameras.
Very detailed description of this camera can be found at the Rick Oleson's web-site.