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.