The list below represents a bunch of FREE handpicked tools/services mobile developers can use/integrate with their mobile applications, if you would like to add a new category/service, feel free to send a PR
- [Prototyping & Mockups] (#prototyping--mockups)
- [UI & UX] (#ui--ux)
- [Documentation] (#documentation)
- [Testing] (#testing)
- [BaaS] (#baas)
- Analytics
- Notifications
- Monetization
- [Showcase] (#showcase)
- Payments
- SMS
- Crash & Exceptions handling
- Icons generation
- General guidance
- https://www.fluidui.com/ - Fast and friendly mobile prototyping, 1 project free up to 10 pages
- http://www.invisionapp.com/ - 1 project free
- http://www.justinmind.com/ - Interactive prototyping for mobile and web on MacOSX, Free
- https://facebook.github.io/origami/ - free forever
- http://pttrns.com/ - UI inspiration for your next iOS & Android app, all for free
- https://www.cocoacontrols.com/ - thousands of opensource and commercial UI controls for iOS
- https://android-arsenal.com/ - Free custom UI controls for Android
- https://github.com/wasabeef/awesome-android-ui - a curated list of Android UI components
- https://github.com/cjwirth/awesome-ios-ui - a curated list of iOS UI components
- http://uxchecklist.github.io/ - a full UX checklist
- https://kapeli.com/dash - API Documentation browswer
- https://testfairy.com/ - Android/iOS beta testing, free up to 100 testers
- https://developer.android.com/distribute/googleplay/developer-console.html#alpha-beta - Google play Android beta testing
- http://ubertesters.com/ - Complete mobile app testing - free up to 5 members with unlimited testers
- https://parse.com/ - simple and flexible, 20GB data storage/database for free
- http://azure.microsoft.com/en-us/services/app-service/mobile/, build engaging mobile apps, free / pay as you go
- https://www.firebase.com/ - Build realtime apps, free plan available
- https://pusher.com/ - build real-time apps, free plan includes 20 max connections, 100k messages per day
- https://layer.com/ - communication backend - Free plan includes 1,000 monthly active users, 1GB data transfer
- https://backendless.com/ - free plan available
- http://aws.amazon.com/mobile/ - one year free plan, then you pay as you go
- http://aws.amazon.com/lambda/ - scalable mobile backend, part of the AWS family, SDK available on both Android & iOS
- https://www.appannie.com - analyze you app store sales data, free plan available
- https://mixpanel.com - mobile analytics, free up to 25,000 data points
- https://keen.io - Analytics for developers, free up to 50,000 event/month
- http://www.google.com/analytics/mobile/
- https://parse.com/ - simple and flexible, free for 1M unique recipients
- https://onesignal.com/ - High volume push notification delivery, unlimited devices/notifications
- http://www.pushapps.mobi/ - Free for 1M push/ month
- https://boxcar.io/developer - Free for 200 PPM (push per minute)
- https://www.pushwoosh.com/ - Free for 1M device
- http://quickblox.com/ - Free for 20,000 monthly active users
- http://www.startapp.com/ - Mobile apps advertising, more than 100K apps in the network
- https://developers.google.com/mobile-ads-sdk/ - Google mobile Ads
- http://www.kiip.me/developers/ - Make rewarding moments in your app
- https://www.heyzap.com/, Transparent mediation on premium Ad network (iAd, Admob ..)
- https://play.google.com/store/apps/details?id=com.nll.screenrecorder - Free screen recorder app available on Android
- https://vine.co/ - six seconds videos to show your incremental app features, Available on iOS & Android
- https://stripe.com/ - Mobile payment built for developers, 2.9% + 30¢ per successful charge
- https://www.braintreepayments.com/landing/mobile-payments - full-stack mobile payments platform
- https://fortumo.com/ - Carrier billing for mobile applications
- https://www.nexmo.com/ - APIs for SMS, Voice and phone verificatin, free trial then pay as you go
- https://www.twilio.com/ - build voice and SMS powered application, free trial then pay as you go
- http://digitimate.com/ - verify user's mobile numbers via SMS, free and open source
- http://try.crashlytics.com/ - no more sad apps, available for free on invite
- https://bugsnag.com , 14 days trial then starts at 29$/month
- http://www.crittercism.com/ - Free up to 30k monthly average users
- http://makeappicon.com/ - all icon sizes available
- http://iconion.com/ - Free icon maker, available on Windows
- http://ticons.fokkezb.nl/ - Generate Titanium icon & splash assets
- https://www.google.com/design/icons/index.html - Material design icons generator, export to SVG & PNG
- https://github.com/adamwulf/app-launch-guide - an app pre-launch checklist