Mastercoin / Omni is a digital currency built on top of the Bitcoin blockchain. Its features include the development of a decentralised exchange and the implementation of smart property and savings wallet. The Master Protocol facilitates the creation and trading of smart properties and user currencies as well as other types of smart contracts. Mastercoin enables the Bitcoin eco-system to become more decentralized. The Mastercoin project was launched on 31 July 2013 with a one-month long fundraiser. Those interested in obtaining Mastercoin may send bitcoin to an 'Exodus Address' where the funds collected would be used to fund the development of Mastercoin. Around 500 people invested in Mastercoin sending roughly 5000 bitcoins to the Mastercoin project.
Gapcoin is a new prime number based p2p cryptocurrency, which tries to eliminate the sticking points of other scientific currencies like Primecoin or Riecoin. It's a fork of Satoshi Nakamotos Bitcoin, a decentralized payment system which is independent of banks, governments and other centralized regulators. With Gapcoin, you will be able to anonymously send money around the globe in no time. The big improvement in comparison to Bitcoin is that instead of burning electricity for its own sake, Gapcoins Proof of Work function actually does useful work by searching for large prime gaps