IR range finder

do you think it would be possible to use an ir emitter and detector and some math to calculate the distance from the sensor to an object. kinda like a PING))) sensor but with ir light, cause im not sure if the arduino could measure things as fast as the speed of light.

You can do it on the strength of the returned light signal. However that depends not only on the distance but also the reflectivity of the surface.

Look at these:-
http://www.active-robots.com/products/sensors/sensors-sharp.shtml

im not sure if the arduino could measure things as fast as the speed of light.

I am sure. Not to the accuracy you want.

What Mike said - light travels 1 metre in about 3 nanoseconds.
A 16MHz Arduino has a clock period of 62.5ns.
You can do the arithmetic.

okay so id take that as a no. haha thanks for your help guys

Below is an example of a DIY approach to a laser based range finder:

Nice lateral thinking - not time-of-flight, but back to a parallax rangefinder.
Neat project.