Spoke length caluclators. They have no secret formula, it is 100% trig.
I (and others) found that the results were about 2mm more than necessary. You may have to grind off the excess depending on the rim you buy (some have recessed spoke holes).
I got all my stuff from lickbike.com, if you buy every thing from them they will set you up with the right spokes.
Harris Cyclery will build the wheel for you for an extra $40.
I trued it on the bike (no truing stand), but did buy a park tensionometer.
I mostly used sheldon brown instructions. read carefully and compare your wheel to others you have just to make sure.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.