Building mutually-satisfying partnerships with organizations complementary to yours is one of the most effective marketing strategies I know, and one of the least costly in terms of budget and time.
Begin by defining how partnerships can help you achieve your core marketing goals. Opportunities include content and contact sharing.
Then prioritize no more than ten organizations that share your values, but aren’t directly competitive in the programs/services offered or engaging the same target audiences (sometimes those partnerships have value too, but don’t start there). Partnerships don’t have to be limited to other nonprofit organizations—consider relevant government agencies and for-profit prospects.