You can get GNTs from https://cryptoderivatives.market, a decentralised trustless exchange contract market. Send a small amount first to a contract address to test and check you receive the correct amount of tokens in your sending address. And don't send from an exchange wallet, but from a wallet you control, e.g., using Ethereum Wallet, https://www.myetherwallet.com or Parity. Users don't pay any fees except for the standard Ethereum transaction gas fees.
This site will soon allow for the listing of purchase and/or sale contracts on ERC20 compliant tokens.
Disclosure: I run this website.
Also, there is a 105108 ETH Bug Bounty on the new upcoming smart contracts.
Other sources of information for unlisted tokens - https://www.reddit.com/r/ethtrader/ and slack forums for the project, e.g. http://golemproject.org:3000 .