Cycloidal gears

http://mysite.du.edu/~etuttle/tech/cycloid.htm

http://garysclocks.sawdustcorner.com/gears.html

http://www.ceet.niu.edu/faculty/kim/mee430/documents/Cycloidal%20Gear.htm

http://users.qldnet.com.au/~ajay/From%20an%20Engineer%27s%20Notebook/GEARCUT.pdf

Cycloid Gear Calculator

http://www.ryerson.ca/~v7chan/cncproject/gear/Cycloid%20Gear%20Calculator.html

http://www.csparks.com/watchmaking/CycloidalGears/

Special gears:
http://switzernet.com/people/emin-gabrielyan/100512-gear-engine/

Cycloidal Gearing is Obsolete – A Personal View
http://www.csparks.com/watchmaking/CycloidalGears/RichardThoen.xhtml

As George Grant put it in his book: A Treatise on Gear Wheels, first published in 1890

Free Software:
http://www.hessmer.org/blog/2012/01/28/cycloidal-gear-builder/
To open the svg-files you can use Inkscape and export it to dxf-files with it. To draw gears with Inkscape you can follow this tutorial:
http://www.wikihow.com/Draw-Gears-in-Inkscape

More gears for Inkscape:
http://www.cnc-club.ru/forum/viewtopic.php?f=33&t=434#p2500

http://www.cnc-club.ru/forum/viewtopic.php?f=33&t=433

http://www.forestmoon.com/software/GearDXF/

http://woodgears.ca/gear_cutting/template.html

http://www.idleamusements.com/?page_id=54

Software:
http://www.delphusa.com/

http://gearotic.com/

Article:
http://brianlawswoodenclocks.blogspot.de/2013/02/gear-design-software.html

Making of:
http://woodgears.ca/gear_cutting/plywood_gears.html

http://inkscapetutorials.wordpress.com/2008/05/01/drawing-gears-in-inkscape-a-howto-by-nicu/