Alternative Internet--what's possible?

It's early in the morning, and I decided to prepare for an imaginary post-apocalyptic scenario. The internet is really helpful and if it went down due to government interference or whatever, it would be nice to have access to something like it to communicate with others and share data. Any ideas?

I went to r/hacking and someone mentioned HamNet, which I guess uses HAM radio, and they also mentioned packet radio. Man, I need to learn more about technology.