Amazon AWS offers free credits to non-profits, there are two ways of accessing these:

1. Apply via TechSoup to receive $2000 worth of credits, this is open to all registered non-profits and has a $175 admin charge
2. Speak to AWS direct, you may be eligible for additional credits depending on your circumstances. Take a look here or get in touch so we can connect you with a representative in your territory.
3. You can also make use of the AWS free tier available to all users, see more details here.