Ethereum: Had 40x growth rate over the last two years. Allows to build fully-functional applications on blockchain without middlemen. Extremely promising currency, solid team (take a look at what Vitalik Buterin is doing right now). #2 crypto right now but still 1/10 of the Bitcoin value.
Monero: Anonymous / private Bitcoin. Now, you may think, What are you talking about, the BTC is anonymous already? which is a very unfortunate albeit popular misconception. All BTC transactions can be seen by the public. For example, by giving out your wallet address to someone, the person is able to see all the payments youve received and sent. The black market (drug dealers and weapon manufacturers) created a solution for this: basically a software that mixes your coins with other coins. Nevertheless, the software needs to be trusted and may not work correctly.
Factom: A blockchain-based system thats optimized to store millions of realtime records with a single hash. Useful for all kinds of business apps. Runs on top of Bitcoin.
Counterparty: A simple description of it may sound like an Ethereum competitor backed by Bitcoin blockchain.
Siacoin: Distributed data storage. An alternative to Box, Google Drive. The big corporations would not have any access to your data in this point.
Lisk: A JavaScript-based Ethereum competitor that aims to make the deployment and development easy. Interesting solution for an internet of things device from a simplicity perspective.