I have created a plugin that can produce a helix and give it a profile automatically. You can download it here:

http://www.freesketchupplugins.co.uk/springtool.php

The plugin on 1001 bits is nothing to do with me. This one is freeware, not a trial:
http://www.freesketchupplugins.co.uk/springtool.php

I'm in the process of making a plugin that will allow you to create highly customizable curved or spiral staircases. Click on the link below for more information.

http://www.freesketchupplugins.co.uk/spiral_staircase.php

I'm currently working on a plugin that can produce a highly customizable curved or spiral staircase in SketchUp.
I hope to release it soon, but in the meantime, take a look at this page:
http://www.freesketchupplugins.co.uk/spiral_staircase.php

As for a helix, I also have a tool that will make one. Unlike helix.rb or drawhelix13.rb, this will automatically give it a thickness based on a value you can specify. http://www.freesketchupplugins.co.uk/springtool.php