During the shoot from this weekend, I was initially guessing at the velocity of my rounds as I hadn't clocked them yet. I use JBM Ballistics calculators when I'm at home and have internet connection, and in the field I use Point Blank software on my netbook.
My guestimates got me in the ballpark, and the Point Blank gave me drop in inches for some of the other shooters with me so that they could get close as well. I didn't have much data for the others except for a few velocity readings, so it was hard to get them on target. My only problem with Point Blank is that I use Mils for the 308 and MOA for my AR. I could do the math and get the solutions, but I didn't have enough data at the time to do that.
Yesterday I downloaded the Shooter Ballistics Calculator for my Samsung phone which uses the Droid OS, and it's fantastic. Entering all my load information from my data book from this weekend and comparing it to the actual results from the shoot, and it's spot on. There's also some other cool gadgets in Shooter to help you get results, and it will give it to you in whatever measurement you desire. Feed it good information and it will provide you with a good solution so that you can blast grapefruit at distance.
Best ten bucks I ever spent!