I don't know if I could have survived my early EE life without this guy. Originally WWII vintage, it calculates reactance and resonance via a slide rule. Luckily, I scanned an only slightly damaged version awhile back, so you can make your own by printing these images out, and using a little cardboard to make the slide, spaces etc. It's not rocket science, but it saved me tons of hours to get close on things, and get a feel for scale.
Sadly, the .gifs I scanned are too large to just include here, so I put them at this link: http://www.coultersmithing.com/data/sliderule.zip
Just unzip these, print them (color is nice) and make your slide rule. It's worth it. Yes, the accuracy with this is in the ~2% range - which is about as good as the components you could buy then were...for a lot of things, it's plenty good enough.