A roundup of links that got us excited this week:

Tree of Codes and the Web It Left Behind

Jonathan Safran Foer turns reading into an experience in his new book, Tree of Codes – something that even digital rarely accomplishes. The book is die-cut to reveal only a handful of words and phrases on each page. On today’s design dominated web, we tend to use technology to tell stories, rather than to help shape them. BBH Labs’ (and Big Spaceship alum) Jessica Berta points to some digital reading experiences she likes, all of which share a UX focus.

Viber For iPhone Aims To Rival Skype’s App

This month, Viber launched an iPhone application that allows you to make 100% free calls to other users over 3G and WiFi. Viber uses less battery power than Skype, allowing it to stay “on” in the background (and hence available for free phone calls). Less than a year old, Viber could prove to be formidable competition for Skype.

Nike Launches Open Source App To Encourage Sustainable Design

Nike Environmental Apparel Design Tool is the latest attempt by the Oregon-based shoe company to promote sustainable business practices. Enabling manufactures to evaluate waste, energy, pollutants, and water in materials and manufacturing, the idea is to help fellow manufacturers find new strategies to decrease their environmental impact.

Krrb

Krrb is a free, location-based social network that lets you buy, sell, trade, or even give to your neighbors in person. Krrb calls itself “enable commerce,” allowing individuals to have meaningful and face-to-face interactions with their local community through the help of the Internet. At first it appears to be a simple reinvention of Craigslist, but its membership process may be the key in proving a sustainable differentiation.

Foursquare on Brink of Adding Photo Sharing, Opens API To Public

Foursquare had a big week this week, seemingly working on a new photo-sharing feature as well as formally unveiling their API to the public. Photo sharing has long been requested by users and the timing feels inevitable as new startups like Foodspotting and Instagram already incorporate location-based apps with photo-sharing.

Twitter Used By 8 Percent of American Internet Users

While it may seem that every man, woman and company is on Twitter, the truth is only 8% of American Internet users, or 175 million users, actually are. If you consider that 74% of Americans are using the Internet, that equates to only 6% of the population on Twitter.