Here is a list of some great design and inspiration resources that we have used. They are as applicable for both startups and larger organizations looking to develop new products and services.
Google Design Staff Blog
IDEO Human Centered Design Toolkit
Stanford d.school Methods Cards
Board of Innovation Revenue Model Inspiration (Examples of Successful and Unsuccessful Revenue Models)
Stanford d.school Bootcamp Bootleg
Designing by Analogy (Academic Paper by J. Linsey, A. Markman, K. Wood) http://www.sutd.edu.sg/cmsresource/idc/papers/2012-_Design_by_Analogy_-A_Study_of_the_WordTree_Method_for_Problem_Re-Representation.pdf