All users of Office 365 have just had their mailbox sizes doubled from the standard 25Gb to 50Gb. At the same time the kiosk accounts have gone up to 2Gb as well.
New Primary Mailbox Size: 50 Gb
New Shared Mailbox Size: 10 Gb
New Resource Mailbox Size: 10Gb
For more information see the Exchange Online Limits here: http://technet.microsoft.com/en-us/library/exchange-online-limits.aspx