hacknear.me fills the gap that hackathon.io and other websites left: the need for an easy way to find a hackathon group based on proximity. It doesn't require someone to make a hackathon beforehand—you don't even have to use it for a hackathon. hacknear.me uses your geolocation to find all nearby coders who are using the app, along with the projects they've made.
It's easy to log in (with GitHub) and even easier to create, manage, and join groups. There's even an IRC built into the site, so you can chat with users to determine whether you want them in your group or not.
There's also a "caffeine run" feature. Coders want to keep coding; they don't want to go and get coffee. Why not let Postmates deliver that Starbucks for you? Using the location of every Starbucks available (this data was scraped), you can find all Starbucks within 3 miles of your geolocation [html5]. Postmates made it easy to set up an ordering and delivery system.