I have taken part in quite a few crowdsourced projects for the localization/qa of some apps for big companies (Disney, google, audi). would mentioning these projects in my - sadly poor - resume increase my chances of netting a job?
Absolutely. As long as you can back up your contributions in some way then it'd be a good idea to include any useful and on-topic experience you've had at other companies.
That type of experience shows willingness to learn and to contribute to projects in your own time. If you've contributed code or indeed language translations it shows off your abilities and where you're currently at professionally.