Descartes' dualism, "Cartesian dualism" started the modern argument about the "mind-body" problem. Descartes suggested that the body is a machine, materialistic; and that the mind is metaphysical. He said that the mind can control the body, but the body can influence the mind.
Spinoza was not a dualist. Initially, he followed Descartes' dualism, but came to think that mind and body are all made of the same substance: monism. He claimed that God and Nature are the same, and that even God is not separate from the one system of which everything is made: in other words, God (or Nature) is the system, a determined system.
For Locke, from what I remember, the jury is always going to be out as to whether he was a dualist. I'd consider him an agnostic as far as dualism goes with respect to epistemology - knowledge (not necessarily with respect to religion): he couldn't prove metaphysical things existed, so he supposed that even if they did, it was irrelevant to the understanding of reality since we couldn't know for sure. In other, words, humans just didn't have the ability to understand the complexities of the mind and what a 'thought' or a 'concept/idea' is, and until they could do so, why not spend time on more empirical investigations. Locke was an empiricist and relied on sense experience for knowledge. Even if the metaphysical exists, humans apprehend them via their senses, or faculties. So, we are always mediated by our senses, and thus can never really know if it is the experiences of what we might consider metaphysical (qualia) are effects of our own perceptions/senses or if they are metaphysical and simply communicated to us by way of our senses.