I thought it might be a good idea to make a list of short, one-sentence descriptions/summaries of the top altcoins and assets on CoinMarketCap. This idea isn't new, but most of the existing lists out there are old and outdated. Of course, it's possible to search the name of each coin/asset on Google and go through the links one by one or read through their [ANN] threads but this can be a rather tedious process. So I think this would save people some time.

Since the list is always changing, I'll try to update it every few days/weeks.

The coins/assets in red are ones that I don't know much about, so they currently lack a description. I might add their description later on. Or feel free to suggest a short, one-sentence description and I'll add it to the list. If there are any mistakes or I've left something important out, then feel free to point it out as well.

Bitcoin: The original cryptocurrency
Ethereum: Decentralized application platform for running 'smart contracts' (i.e. code on the blockchain)
Ripple: Distributed peer-to-peer payment network and currency exchange for financial institutions
Litecoin: Cheaper and faster transactions than Bitcoin
Dash: Anonymous coin with decentralized mixing, fast transactions, and decentralized governance
Monero: Anonymous coin (fork of Bytecoin - see below) with fairer distribution
Ethereum Classic: Variant of Ethereum where a large amount of hacked funds were not returned to investors
NEM: NXT-inspired coin with modified PoS system ("proof-of-importance") and wider initial distribution
Augur: Decentralized prediction markets built on Ethereum
MaidSafeCoin: Token to be exchanged for Safecoin once the SAFE Network (a decentralized data storage and communication platform) goes live

Golem: Decentralized Ethereum-based computation network for buying/selling computing power
Zcash: Anonymous coin where transactions are verified without the sender/receiver and amount transferred being known (zero-knowledge proofs)
Tether: Blockchain-based representation of the US dollar backed by fiat reserves
Dogecoin: First meme-based coin
Decred: Community-directed cryptocurrency with decentralized governance
PIVX: Dash fork
Stratis: Customizable blockchain-as-a-service (BaaS) C# development platform for businesses and organizations
Waves: Platform for creating and trading tokens on a decentralized asset exchange
Factom: Blockchain-based record-keeping system
Steem: Reddit-esque social networking/blogging platform

Iconomi:
DigixDAO:
BitConnect: HYIP-esque lending platform with trading bot
SingularDTV:
Round: Decentralized Ethereum-based eSports platform
Lisk: Decentralized Javascript application platform
First Blood: Decentralized Ethereum-based eSports platform
Bytecoin: Anonymous coin and the first to use CryptoNote technology (ring signatures)
GameCredits: Coin for the gaming industry (in-app or in-game purchases)
BitShares: Decentralized cryptocurrency and crypto-asset exchange

Miscellaneous coins not in the top 30:

Auroracoin: Coin for Icelandic residents
Burst: Coin mined using free hard drive space ("proof-of-capacity")
Gridcoin: Coins rewarded for contribution to BOINC network
Huntercoin: Human-mineable coin where coins are harvested by playing a game
Namecoin: Decentralized Domain Name System (DNS)
NXT: First pure proof-of-stake coin
Omni: Platform for creating custom assets/currencies on top of the Bitcoin blockchain
Peercoin: First coin to use proof-of-stake (actually hybrid PoW/PoS)
Primecoin: Coin with proof-of-work system that searches for prime numbers
RISE: Lisk fork