The Peace and Collaborative Development Network provides a great deal of free resources. This includes job listings and other opportunities.
There is also a fee-based platform called Career Campus that has expert support, community, and curated content.
Getting Background on NGOS and non-profits is an important part of your job search. Below are resources that can assist you in doing this work.
International Development Jobs for Young Professionals
A great resource to check out is the Business Research Guide. It offers tools and directions on best searching practices in business-related databases.