Without a doubt, see the film "Side by Side" to give you some inspiration for the last few decades. It's pretty basic but it covers the transition from film to digital. And indeed, digital is a big part of the independent movement due to affordability and ease of use. You will have to do research into before the DSLR movement (might wanna ask the DVXusers forum). But for DSLR this is what I know:
As for DSLRs, it started with the 5D Mark II when Canon added a video function. Vincent Laforet released a short piece called "Reverie" that was supposedly the first to make it popular. People say it is because of the shallow depth of field that made it popular. But it was a number of things combined that made it an attractive package- a small form factor, price, accessibility, hybrid between stills/video, and interchangeable lenses.
Since then, one of the major contributors to independent filmmakers is the group Magic Lantern. They hacked the Canon camera's firmware to give features (peaking, zebras, custom ISOs, etc.) that normally are in video cameras only. You also have picture profile creators, the unsung heroes that have made the cameras sensors respond much better. See Cinestyle picture style, Visioncolor picture style, Cinema picture style, FLAAT, Marvel picture style, etc.
Then there's a group that hacked the Panasonic GH2, another well liked camera for pretty much the same reasons as the 5D Mark II except cheaper. This hack made the camera's bit rate very high, and it was exceptionally good quality for the price at that time.
You can't just have a cheap camera and save money. Filmmaking equipment is notoriously expensive. A number of American, Chinese, and even Indian manufacturers have created low budget alternatives. Kickstarter people have funded such projects too - see the $50 follow focus by Hondo Garage.
YouTube is known for showing a lot of DIY equipment and tutorials for filmmaking. Vimeo is obvious - its a platform that allows people to distribute their material in an artistic space immediately and not wait for approval of distribution. Facebook/Twitter have lots of communities, but I can't name anything special that is different in this industry.
Just as an example, Technicolor Cinestyle Assist released a $99 grading program. At that price, you can guess who they are targeting. There's a ton of plugins as well that are pretty cheap. Other than that, NLE /editing software is expensive.
I don't think ARRI does anything here.
RED once promised 3K resolution for $3K, which was never fulfilled. Their cameras are still too expensive for independent filmmakers.
Blackmagic, normally a camera accessory/software company, soon became a camera maker to fulfill this gap that RED left open. They released the Blackmagic Cinema Camera, 2.5K for $3K. They also added RAW capability, and what is basically considered the most beautiful image for the price (with compromise for other things).