Gravity in 2d Games
I always wished to know how exactly do creators Mario, Contra and Kirby (Specially this one) program gravity. Having done with the s = ut + 0.5 * at^2 and such forumulae, I haven't yet made a perfect framework for simple gravity physics, bounces and collision reactions. But, here is an article from The Science Creative Quarterly - link that really satisfies me with a historic look and clever analysis of the gravity in Mario.
Some more places to checkout for game physics-
http://www.codeplex.com/FarseerPhysics -- good for .NET developers