Prowess Amplifiers offers resources for the guitar tube amplifier builder. We have a huge schematics inventory, projects section and forum.

http://www.prowessamplifiers.com/      (popularity:  ; clicks: 0; comments: 0)      

Online unit conversions from physics units to other physics units.

http://www.asknumbers.com      (popularity:  ; clicks: 0; comments: 0)