ggplot2 Cheat Sheet:
Basics

library(ggplot2)

Empty Axes

p <- ggplot(data = mpg, aes(x = cty, y = hwy))
print(p)

A Quick Example

p <- qplot(x = cty, y = hwy, data = mpg, geom = "point")
print(p)

Blank Axes

p <- ggplot(economics, aes(date, unemploy))
p <- p + geom_blank()
print(p)