Creddon - Tweet for a cause and a sponsor will donate $1 to charity
All or Nothing - Competitive donations for causes you care about.
Send Mail Get Mail - A postcard-sending website.
Public Design Vault - 500+ design tools for public good, all in one place
Postacard - Text a photo to send it as a postcard for $3.
Delightful - Delightful is a simple gratitude journal to spark a passion for self-reflection!