Lean Startup - 

http://theleanstartup.com/principles

http://www.deviantbits.com/blog/the-lean-startup-in-a-nutshell-i-foundations.html

Minimum Viable Product - 

A Minimum Viable Product has just those features that allow the product to be deployed, and no more. The product is typically deployed to a subset of possible customers, such as early adopters that are thought to be more forgiving, more likely to give feedback, and able to grasp a product vision from an early prototype or marketing information. It is a strategy targeted at avoiding building products that customers do not want, that seeks to maximize the information learned about the customer per dollar spent. "The minimum viable product is that version of a new product which allows a team to collect the maximum amount of validated learning about customers with the least effort." The definition's use of the words maximum and minimum means it is decidedly not formulaic. It requires judgment to figure out, for any given context, what MVP makes sense.

For additional context and competing definitions, see Minimum Viable Product Cheat Sheet.

Business Model Canvas - 

http://en.wikipedia.org/wiki/Business_Model_Canvas

http://grasshopperherder.com/business-model-canvas-for-puppies-part-i/ 

validated learning -

http://en.wikipedia.org/wiki/Validated_learning

http://www.startuplessonslearned.com/2009/04/validated-learning-about-customers.html

Product/Market Fit -

http://www.stanford.edu/class/ee204/ProductMarketFit.html

http://www.quora.com/How-do-you-define-Product-Market-Fit

http://bestengagingcommunities.com/2012/04/25/what-makes-a-product-fit-a-market-or-how-to-achieve-product-market-fit/

https://davidcummings.org/2013/07/04/5-ways-to-identify-product-market-fit/

Product Development -

http://en.wikipedia.org/wiki/New_product_development

Customer Development -

http://www.startuplessonslearned.com/2008/11/what-is-customer-development.html