I use Spocalc, BUT I use my dimensions not theirs. Not sure why it does it the way it does. I also cross check with the one that Zaphod linked to. I am anal, I don't like the spoke ends protruding beyond the nipple if I can help it. I cut them off with bull nose nippers and then dress the end with a dremel tool.

Tension gauge. I use it mainly as a verification tool, or if I get a set of wheels that I didn't build up. On most of my wheels I aim for somewhere in the middle to high end of the chart. NOT maximum tension, I want some wiggle room. On just about all of my wheels I can get a round, true wheel and have the tension readings plus or minus 10%, usually closer. On older wheels that have seen rough use, I don't worry as much about it as long as they are close.

+1 on relieving the spokes as you tension up the wheel, there are a variety of methods, grabbing spokes, putting long screw driver across pairs of spokes, putting the wheel on the floor and pressing down on the rim, etc.

Aaron