EDIT: Modified suggestion with clipboard example (see comments):
I'll put my 2¢ in and say that I'm a fan of the "form-and-pencil" icon, since you do collect quite a bit of information (more than a simple "like" button).
(Found: http://learn.senecac.on.ca/~asharma68/form.html )
(Found: http://www.athlete-inside-blog.com/2011/02/15/transitioning-to-outdoor-running/)