My partner and I wanted to have a video on the landing page that explains our startup. Is there any crowdsourcing for videos out there? How do usually startups get someone to make a video for them?
This is a great question. i'm following it as I'd probably need the same kind of service soon. If for some reason the solutions you stumble across are too expensive, consider doing what I've seen others do: Use screen capture software to run through a demo of your product narrated by you - and then have a professional voiceover person replace your voice with his or hers. You do this by "writing a script" where you go over your product, explaining it- then capture a demo done by you. Some of those screen capture software packages let you add embedded text, titles, etc. Pretty easy to use - the only thing that you'd really need is a good voiceover artist - and those are not expensive and usually hungry... googling voiceover artist would yield plenty in your area I'm sure.
We did this by finding a friend of a friend who's a performer and "a bit famous" (the Six Degrees of Kevin Bacon and all that), giving them a HD camera and seeing what happened. Obviously, the result wasn't a technical exposition of the product but it was a fun clip that got the basic concept across. We used that video for a couple of years.
Or, do what ron M. suggests and make a screencast (script, practice, practice, practice, many takes, a lot of editing) and get a friend with a deep voice or a British accent to do a voiceover.