n0tice is a simple location based public notice board system. It's completely open and unfiltered, and allows users to post any sort of notice they want, tagged with their location, and lets them read notices near them, sorted by distance. Quite a simple little idea, and if it gets a user base, it could end up being quite useful. Although first designed for iPhone, the n0tice API was quickly released to allow integration into other programs, including desktop apps.
Some may remember yfrog as the photo sharing service previously associated with Twitter. However, since Twitter's launch of it's own internal photo sharing service last year, Yfrog has been left worse for wear. Despite the effects of this, Jack Levin (ImageShack founder) has not accepted defeat and has bravely entered the social networking arena to meet the giants face to face.
Berlin start-up Readmill, is providing a platform for eBooks that connects readers regardless of what platform they are using. Readmill's core offering is a free bookreader that competes head to head with Amazon’s and Apple’s offerings. Unlike other eReaders, Readmill is based on a device-neutral, API-driven platform that integrates social recommendations, annotations and geolocation services.