iPhone has brewpal which my wife and I use religiously. We used to use pro-mash and beer smith, but since we both have iPhones and iPads, the computers get little attention anymore. Everything is done from the tablet or the phone. Here's a list of what's in my "brewing apps folder."
BJCP guidelines: free app that gives you all the style guidelines of beer you want to make.
Brewpedia: an app that gives you definitions and descriptions of all malt and hops on the market.
Brewpal: A great app for creating and fine tuning recipes.
Get hoppy: An app that tells you the AA, purpose, and substitute of each hop variety.
BN Mobil: The brewing network's free app to listen live and streaming all the archive shows.