From clouds in the sky to fish in the ocean, X Stock Video provides HD stock video for free (mostly). They have many categories, including abstract, food, nature, and many more.
Type: Abstract, animals, buildings, food, holidays, nature, people, tech, etc.
If stock footage is what you want and free is what you want to pay, try Stock Footage For Free.
Type: Looping, nature, people, slow motion, time lapse, etc.
Pond 5 is a nice resource for most royalty-free assets including video, music, sound effects, 3d models, images, and after effects assets. They've got quite the library, so worth a stop if you need something for your project!
Type: Video, music, sound effects, 3d models, images, after effects
While Blink Farm is primarily a youtube resource for sound effect, it also has some stock video that you can use.
Type: Explosions, music, other video assets
Cutest Stock Footage has light leaks, old film effects, and much more. It's another huge library that you might find useful in your video project.
Type: Light leaks, old film, film burn, overlays, particles, abstract, etc.
Although Shutter Stock isn't free, it is a great resource if you're looking for quality b-roll.
Type: Video, music, photos, vectors, etc.
Story & Heart provides high quality video of people doing random things, for a price.
Type: People, b-roll
iStock isn't free, but it's another option available to search, similar to shutter stock.
Type: Video, audio, photos, vectors, etc.
Videvo offers free stock footage and motion graphics.
Type: B-roll, stock footage
Videoblocks is a membership site (not free) that offers what could otherwise be considered expensive footage for a subscription fee.
Type: B-roll, stock footage
Mazwai uses a nice and simple interface to show their free videos.
Type: B-roll, people
Distill will send you 10 free HD videos every 10 days for commercial or personal use for free.
Type: B-roll, stock video
BRoll has exactly what the name implied: b-roll!
Type: B-roll, stock video
This site has some videos that don't have any copyright restrictions, are uploaded weekly, and can be downloaded for free.
Type: City, sky-line, landscape
Some more (free) stock footage can be found on Clip Canvas.
Type: City, sky-line, landscape, b-roll, stock video
Although the site isn't exactly ideal (it uses Google Blogger), it gets the job done and offers a great service of free stock footage clips. Browse their selection on Youtube to see what type of videos they have.
Type: Nature, animals, b-roll
Videezy is a search engine for free royalty-free videos, but you can also browse around to see what stlye of videos they offer.
Type: Nature, b-roll, stock video
Footage Freaks have a good selection of stock footage, but they also have photos, sound effects, and other assets.
Type: Stock video, animals, landscape, photos, sound effects
Motion Elements offers some free stock footage on a weekly basis, so they might just have what you're looking for.
Type: Stock video