Here are some solid tools to help you with the processes of brainstorming and syntheses.
Open IDEO Brainstorm in a Box This is a great resource for learning the process of translating insights into opportunities.
Design Kit – Ideation: Solid resource for learning the process of ideation, brainstorming, co-creation and concept development IDEO-style.
IDEO HCD Toolkit Also a great brainstorm and synthesis guide that is super-easy to use (begins on page 81)
Stanford University d.school Brainstorming Rules A helpful cheat sheet for setting-up a brainstorming session.
Slideshare Presentation posted by gfrulonge on the process of ideation and synthesis. A useful (and brief) walk-through of the d.school process.