Many techniques have been proposed in the past for using acousto-optic devices to perform signal correlation. This paper reviews these techniques and discusses the design tradeoffs involved in choosing a particular configuration for a given application. Configurations are classed as two major types. The first type, spatial integrating correlators, perform correlation by integrating light diffracted by all parts of the signal(s) which are simulataneously present in the acoustic device. This type of correlator has a large range window, but the time bandwidth product is limited by device parameters. The second type, time integrating correlators, use a detector array to perform an integration in time for each point within the cell. This provides a limited range window but a large time bandwidth product. Results obtained with both types of systems are shown, along with pictures of fabricated hardware. Acousto-optic device parameters are also summarized for comparison with competitive technologies.