MarcusI didn't watch many talks at #35c3 but one I attended and can highly recommend was by #FDroid core team member _hc about nearby and offline connectivity:
https://media.ccc.de/v/35c3-9595-wind_off-grid_services_for_everyday_people
Jonkman Microblog is a social network, courtesy of SOBAC Microcomputer Services. It runs on GNU social, version 1.2.0-beta5, available under the GNU Affero General Public License.
All Jonkman Microblog content and data are available under the Creative Commons Attribution 3.0 license.