ZURB is a self professed team of "T-Shaped Designers that help grow businesses" and doesn't fit into typical agency categories. They have worked with a ton of startups since 1998 and have help build or refine some of the greatest UX you have experienced across names big and small.
They are situated geographically in the city of Campbell, which is a small community in the South Bay Area which is in the heart of the Silicon Valley. One of the things that makes ZURB very unique is how transparent they are in their process and their tools.
If you are interested in Responsive Web Design or
User Experience or even Sketching Wireframes ZURB has you covered. They not only post amazing articles that offer a lot of value and insight but they also host free events such as their Soapbox and the Foundation Meetup allowing the community to tap into their hive mind and get a glimpse at how the masters work at their craft.
So you might be thinking that Foundation looks a lot like
A common misconception is that Foundation is for designers and needs a lot of design to work well, where as Bootstrap just looks great out of the box. One can certainly argue that Bootstrap is a little more "designed" out of the box and Foundation looks a little more bare bones.
At first it appears that Bootstrap seems to be clear winner when making a choice. The problem comes later, after implementing Bootstrap on a project and you want to make some large sweeping changes. Sure, this is possible with Bootstrap but it often leads to a lot of overridden CSS or other less graceful solutions.
Foundation uses Sass and allows you to easily and quickly change the color, appearance and style of elements. It is designed to be configurable, flexible and extensible.
In my experience, ZURB Foundation is fun to work with. But, lets see if I can qualify why I think it is fun.
You hear a lot of these same types of comparisons with the Ruby language and the Ruby on Rails framework that popularized it. Things like Syntactic Sugar, Magic and Readable are thrown around. It is something that is hard to explain to people who 1) have not programmed in another language that is not so fun like C or Java and 2) moved to Ruby and Ruby on Rails and 3) experienced the culture of Rails.
Coming back to Foundation it is both the syntax, structure of the framework but most importantly the culture that surrounds it that makes it so much fun.
First off, ZURB is a fun company. Look at the bright colors or the playful and energetic writing style they use.
They are passionate, quirky and fun. Just take a look at their about page or one of their ZURB Wired projects where they build out a project for a deserving charity in a company wide 48 hour marathon.
When you look at Bootstrap in comparison, it is not that it is wrong or right it is just that it is a different culture. Bootstrap presents itself as a mature, corporate and mild mannered framework.
Which brings us to the Yeti. Whats up with the Yeti and what does that mean anyways?
Well, ZURB offers a explanation, but I think the Yeti is much more.
The Yeti is really the mascot for ZURB Foundation and is lovingly crafted by some of its best designers. There is even ZURB swag if you are lucky enough to get your hands on it. There are stickers, T-Shirts and other Yeti sightings.
If you want to learn more about ZURB, Yetis and ZURB Foundation I suggest taking a look at their official history.
UPDATE: A special thanks to @Brandon_Arnold for pointing out that ZURB is in all caps.