A global network of satellite ground stations, designed as an open source participatory project. A machine readable crowdsourced satellite information database. Built from readily available and affordable tools and resources. Concentrates on satellites in LEO. A significant amount of work is involved so you won't be able to just throw up an RTL-SDR and get going. Designed to be built using readily available materials and access to basic tools and machinery using 3D printers and CNC as provided by average hackerspaces.
Software for investigating unknown wireless protocols. Plug in an SDR and go. Helps you figure out how to demodulate signals, record and transmit signals, generate an overview, write or customize decoding routines to get a clearer picture, annotate and label the signals, fuzz devices (with a transmit-capable SDR), and run simulations of the protocols' state machines.
An AX.25 packet radio chat protocol with support for digital signatures and binary compression. Like IRC over radio. Note that, because encrypted messages are illegal on ham bands, messages are signed to prevent spoofing but are not encrypted. Requires a TNC to send AX.25 - Direwolf is recommended.