Looking for a good general IR Distance sensor

I need a decent generic infrared distance sensor. I see lots of them made by Sharp, they seem to be common. Any suggestions on a simple easy to use one? I'm also wondering which would be easier to interface with, analog or digital sensors? any links (digikey, datasheets) would be appreciated.

Also, is there any math involved in getting a reading in say centimeters or inches. If so, are there any libraries that will do it for me?

DistanceSensing@Playground

I've used a few of the Sharp ones from Sparkfun: http://www.sparkfun.com/commerce/categories.php?c=139

There are 3 for different ranges. They spit out an analog voltage according to the distance, so I would just plug that into analog in on your arduino, and test the range of values. It helps to use something that is white or reflective, IR works nicely with those type of things.

As far as getting readings in inches, refer to the data sheet for the sensor.