Don't know how I missed this thread, I love blockchain and DAG (directed acyclic graph) technologies.
The Good
The obvious one. A distributed and open-source, stack-based, turing-complete virtual machine. I've written a lot of Solidity, it's a neat task to work around managing gas costs, making you want to optimise what you can. If you love solid mathematical proof, read the yellowpaper, it throughly and logically describes the intricacies of the system.
The RingCT, stealth addressing, and ASIC resistance (thanks to CryptoNote). Fungibility is also based.
An in-development competitor to Ethereum. Aims to introduce parallelised processing among nodes to increase execution time (and potentially reduce costs?), among other iimpressive changes. Wants users to not have to pay fees for non-transactions. Governance model is scary though (testnet currently live). Executes/will execute WebAssembly (apparently, I haven't yet installed the testnet).
Disclaimer, I plan to buy about 2kUSD EOS in a couple days
Blockchain-based, decentralised cloud storage, cheaper than amazon and google drive and that. Very cool, still under development but the client and daemon software is available for download. Everything works, too, though it can be buggy. Written entirely in go. Bitmain released an ASIC for it a couple days ago.
EC2 on the blockchain. Currently in alpha, and only does rendering for Blender. Aims to be able to execute all sorts of shit for low fees in future, github is active.
DAG with conditional payments, smart contracts, TOR support, untracable payments, and a host of other guff. Way faster than a blockchain. Very, very cool.