Much like you can earn the qualification in WGSS by strategically choosing electives, you can also earn a Certificate in College Teaching Preparation. The program is free and any Professional student can join (in fact, since you must TF to complete it, you are sort of getting paid to earn an additional certification.)
Info about the Graduate Teaching program is here:
http://www.yale.edu/graduateschool/teaching/
Fundamentals workshop registration is here:
http://fs3.formsite.com/yalegraduateschool/form577549311/index.html
Upon completing the program you will get a transcript notation stating that you have earned a certificate in college teaching through the Graduate School of Arts and Sciences.
To earn the certificate, you must attend a series of workshops, TF a course (only counts if you TF undergrads, not if you TA your peers), be observed teaching twice, observe other people teaching twice, and compile a teaching portfolio.
If you are interested in teaching in the future, it is extremely helpful to be able to prove experience and training to those who are hiring you. Even if you don't have a TF job right now, but plan to apply for one in the future, you can still attend the workshops to get started.