This chapter explores co-production with community groups of innovative digital technologies designed to address challenging social issues. It presents lessons learned from the Catalyst project (http://www.catalystproject.org.uk), which carried out 13 such co-production projects over a three year period developing digital solutions in areas as diverse as homelessness, anxiety management, behaviour change, and renewable energy. The approach taken was to form meaningful partnerships of multidisciplinary academics and external partners from community groups. The chapter offers guidelines for how to make such partnerships effective based on the Catalyst experience. These guidelines cover a range of different areas: working in the community, research innovation, working across disciplines, and practicalities. They are illustrated, where appropriate, by reference to a range of research partnerships set up as part of the Catalyst project.