NeurOS is an open platform for accelerating research, development and hosting execution of intelligent applications. A NeurOS application is a directed ''neural graph'' of modular components connected by signal paths, similar to biological brain connectivity and functional block diagrams of neural pathways. Built-in reusable modules (NeuroBlocks) provide a wide range of general-and special-purpose capabilities: inputs/senses, outputs/effectors, processing, memory, pattern learning and recognition, visualization/instrumentation, custom module development, integrating external intelligence capabilities, and sub-graph reuse. NeurOS sub-graph assemblies address neural/cognitive functions including perception, pattern learning and recognition, working memory, imagination, prediction, context priming, attention, abstraction, classification, associational thinking and behavior. NeurOS applications are inherently portable, scalable, networkable, extensible and embeddable. NeurOS development tools provide simple intuitive graphical drag and drop application assembly from components without programming, along with testing, debugging, monitoring and visualization. Prototype NeurOS applications have begun to explore a wide range of intelligent functions in diverse areas, including aspects of pattern recognition, vision, music, reading, puzzle solving, reasoning, behavior. Building working intelligent systems using NeurOS and NeuroBlocks lets researchers and developers focus on their core functions and rapidly iterate and instrument working models, fostering both analytical and biological insight as well as usable systems.