Gmaps Pedometer: a great Google Maps hack that lets figure just how long that bike ride to work is and even send that route as a link to friends.

NumSum: for those simpler spreadsheets that don't need Excel (i.e. all of them).

Five Ingredient Recipes: when cooking for myself I try not to exceed three steps in my cooking process, which includes unwrapping the package to stick it in the microwave. Five ingredients implies at least five steps, but I may be willing to sacrifice.

Rapid Afterimage: this optical illusion still throws me.