I discovered Bitcoin in May 2011 by seeing a post on Reddit with only 88 upvotes. I only barely came across it and if I hadn't, in all likelihood, I still wouldn't have heard about Bitcoin. Bitcoin caused me to learn about and use TrueCrypt, Tor, and PGP(GPG). But it almost never happened! So that has me worried: What other technologies should I really be aware of and using that I am not using (or that most people are not using)?
Here are the big ones I know about so far:
Bittorrent - Fast peer to peer file distribution
Bitcoin
IRC - Old chat protocol still used
GPG - Message encryption, doesn't rely on any third parties
SSH - Encrypted TCP connections & tunnels between you and a server
TrueCrypt - Easy full-disk encryption and file-container encryption for Windows
Tor - Anonymous TCP connections and connections to hidden-services
I suppose that TrueCrypt is not a protocol but rather a tool, and if we are including tools on this list, then it gets much bigger. But that's Okay! What are your invaluable protocols and tools and what do they do?
EDIT: added links and descriptions per request