From Rival Game Labs:
DicePro is a freeware dice rolling utility for the USR/3Com PalmPilot® PDA. It supports many different die types and can perform many useful die rolling functions automatically such as rerolling dice and totaling subsets. In addition to its flexible general-purpose dice rolling functions, DicePro also understands how to roll dice specifically for the Storyteller system, ShadowRun, Ars Magica, Earthdawn, the HERO System, and others. It supports a wide variety of die types including the standard polyhedrals (4-, 6-, 8-, 10-, 12-, 20-, and 100-sided), generalized N-sided "virtual" polyhedrals, FUDGE dice, and more.