I’m a member of Amnesty International, and I’ve sponsored kids through Plan Canada for about 10 years. I used to be a professional fundraiser, and those two really struck a chord with me.
UNHCR (United Nations High Commission for Refugees) and MSF (Medicines Sans Frontieres) are ones I used to work with, and they both do great work too.
In Canada all registered charities are audited annually. Their financials are available online for you to review.