Google today introduced a graphing functionality on Google search.
Now you can plot mathematical functions right on the search result page. Just type in a function and you'll see an interactive graph on the top of the search results page. For example, here is the graph for the x/2, (x/2)^2, ln(x), cos(pi*x/5):
You can zoom in and out and pan across the plane to explore the function in more detail. You can also draw multiple functions by separating them with commas. This feature covers an extensive range of single variable functions including trigonometric, exponential, logarithmic and their compositions, and is available in modern browsers.