What stimulates innovation?

Boredom
Failure
Incentives
Something is different and "x" no longer works. (where "x" is a method or technique or set of methods/techniques and where "something" is students' age, gender, first language, motivation -- or lack of it, economic class, goals, etc. "Something" could also be the setting -- classroom space, furniture, privacy. noise level, dynalics such as a single teachere with an aide vs. team teaching
New content (subject matter) to teach
New tools or electronic technology available in the classroom such as computer(s), LCD/Multi-media projector, electronic white bpard, or VCR
Math manipulatives for teaching numeracy or ESOL
Changes in world or in the U.S. culture: students' access to the Web at home or work, development of highly motivating video games or simulations for learning, schools' raising standards for graduation in response to the changing nature of work in the world economy
Survival skills increasingly including the ability to use computers and the Web. These changes mean that teachers have to gain new competencies in using and integrating technology in their practice
Some kinds of collaboration
Professional development: new methods of distributed knowledge, reciprocal teaching