Vault.com is now merged with Firsthand and can be found at https://harvardocs.firsthand.co/. Same great resources and some exciting extras, with a more modern and personalized experience!
If this is your first time accessing Firsthand, enter your Harvard affiliated email and press submit. Then, click "Get Advice.", enter your Harvard affiliated email once more, and click "No Password Yet?". Once you complete your login, you can navigate to the "The Library" tab on the left sidebar to access the Vault guides.