I take you on a simple stroll through Lisp's basic constructs and then ramp up quickly. You'll see Lambda expressions, recursion, and macros. This quick tour should give you an appreciation of Lisp's productivity and flexibility.
A gravatar, or globally recognized avatar, is quite simply an 80×80 pixel avatar image that follows you from weblog to weblog appearing beside your name when you comment on gravatar enabled sites.
T. Omori, and K. Maruyama. MSR '08: Proceedings of the 2008 international workshop on Mining software repositories, page 31--34. New York, NY, USA, ACM, (May 2008)