Each service has different limits associated with it. Please see below:
Mail: Each user has 25 GB of storage.
Drive: With the implementation of Google Drive, all users will have 5 GB of storage.
Sites: Embedded documents, including Google Documents, don't count against the Sites storage quota. However, items added as an attachment or to your file cabinet do count against your quota.
Video: Google Video for education offers 10GB free of charge to Google Apps for Education customers. It's not currently possible to purchase additional space.