The majority of soft shell jackets feature a tighter cut, eliminating excess bulky material and making them perfect for sports-themed outings, like hiking, biking, camping, etc. They often feature breathable, stretchy material as well.
Serious surfers know that Quiksilver is one of the best brands out there already, and now that they've joined with the Surfrider Foundation to make 100% organic cotton shorts that are comfortable and breathable, they are even better.
Zero Restriction Featherweight Rain Pull-On pants with Gore-Tex: Although not breathable, these are a lightweight pant that, with a drawstring close, side zippers and ankle-hugger snap system, are designed to keep you completely dry.
No More Diaper Rash-While implying that babies who use cloth diapers never experience diaper rash is a bit of an exaggeration, the soft cotton material is more breathable, making the occurrences of diaper rash less frequent.
The key to being comfortable in a room where hot yoga is practiced is to keep the clothing to a minimum level (whatever minimum you are comfortable with), and make sure that the fabrics are light, stretchy, and breathable.