From weak clients outsourcing computational tasks to more powerful machines, to distributed blockchain nodes needing to agree on the state of the ledger in the presence of adversarial nodes, there is a growing need to efficiently verify the results of computations delegated to untrusted third parties. Verifiable computing is a new and interesting research area that addresses this problem. Recently, new applications of verifiable computing techniques have emerged in blockchain technology for secure key management, sybil-resistance and distributed consensus, and smart contracts, while providing desired performance and privacy guarantees. In this paper, we provide an overview of common methods for verifying computation and present how they are applied to blockchain technology. We group the presented verifiable computing applications into five main application areas, i.e., multiparty approval for secure key management, sybil-resistance and consensus, smart contracts and oracles, scalability, and privacy. The main contribution of this survey is to answer two research questions: 1) what are the main application areas of verifiable computing in blockchain technology, and 2) how are verifiable computing techniques used in major blockchain projects today.