I spoke before about brewing with the iPhone here.  I recently came across this great new app ($4.99) for the iPhone called iBrewMaster (app store link).  This is a great app that brings even more useful brewing tools into the palm of your hand.
The app comes with about 50 or so recipes, but also lets you create and edit your own.  It has a nice selection of grains, hops, adjuncts, and yeast as well as a place to enter notes for the brew.
Also great is a "Schedule" function which tracks your batch and what should be done when (ie: transfer to secondary, bottle, serve, etc).
You enter each batch as you go.  The app auto-calculates a number of things, including ABV% and calories.  You also have the option to enter all of your information regarding OG, temp to ferment at, and duration.
Recent updates added the ability to email a recipe, and also added additional options for sorting recipes, including by color (which is also included when you create a batch).
I'd love to see calculations for amount of water to use and temps, but for now this is a great addition to my brewing space.
Now, during a brew, I can use my iPhone to make unit conversions, control my brewing tunes on the radio, and create and track my batches.  I can also send texts and emails, make phone calls, and surf the web - all without sitting down in front of a computer.