Here you can find the key tools/API/services for your StartUp project:

**We are sure that it will useful for you and save your team's time.
***If you want to add here your tool/API/service, you need to write a post about it and of course to get positive karma!


Trending:
http://www.cobookapp.com - Cobook is a free application that makes contact management enjoyable.
http://www.easel.io - Design For the Web. Easel is an in-browser, high-fidelity web design tool that lets you mockup, share and implement your ideas with ease.

Business Model Canvas:
http://www.businessmodelgeneration.com - iPad Application
http://leancanvas.com
https://www.leanlaunchlab.com
http://bmfiddle.com -

StartUp Combinators/Accelerators:
http://startupsauna.com
http://ycombinator.com
http://hackfwd.com/
http://www.techstars.com

Domain Registration:
http://instantdomainsearch.com
http://www.godaddy.com
http://www.namestation.com

Cross platform mobile development:
www.appcelerator.com
www.phonegap.com
www.sencha.com/products/touch
http://www.theappbuilder.com
http://www.mono-project.com -

UI design and wireframes:
www.justinmind.com
http://uxpin.com -
http://www.sencha.com/products/designer
www.balsamiq.com
www.99design.com
http://cooltext.com -
http://www.shutterstock.com -

Landing page
http://launchrock.com
http://www.kickofflabs.com

Source Code Repositories:
https://bitbucket.org - Free up to 5 team members
https://github.com - Free for open source projects

Lean Startup Tools:
http://list.ly/list/9E-tools-and-services-for-a-lean-startup -

User Feedback
http://www.usertesting.com

Other Tools
50 Fantastic Free Tools For Startups

Gaming
http://cloudmach.com/ - 3D gaming platform in HTML5
http://unity3d.com/

Backend System
https://cloudmine.me easy way to build backend for mobile apps developes
https://www.parse.com mobile SDK provides all the server-side functionality developers need for rich, internet enabled applications.

Web Metrics:
http://www.google.com/analytics
http://mixpanel.com
http://www.kissmetrics.com
http://newrelic.com

Web Heatmap Metrics
https://www.crazyegg.com
www.clicktale.com
http://verifyapp.com

Mobile Testing:
https://testflightapp.com

Mobile Metrics and Analytics:
http://www.flurry.com/
http://finger.mobillify.com
http://www.localytics.com
http://www.capptain.com

Competitors Metrics:
http://www.compete.com
http://www.alexa.com

Email Marketing
http://www.constantcontact.com
http://www.verticalresponse.com
http://mailchimp.com
http://www.madmimi.com

Recommendation Engines:
http://mahout.apache.org

Search Engines:
http://duckduckgo.com
http://blekko.com


Cloud services:
http://www.softlayer.com
http://www.twilio.com
http://aws.amazon.com
http://bitnami.org

Hosting:
http://www.arvixe.com
http://www.rackspace.com
http://www.godaddy.com
http://ipage.com

Grow Fans:
https://www.fanbridge.com


Collect Payments:
https://stripe.com
https://www.wepay.com