Google Apps

Google Apps suite of applications comprises the following:

• Gmail for business 25GB storage, less spam, and a 99.9% uptime SLA, and enhanced email security.
• Google Calendar Agenda management, scheduling, shared online calendars and mobile calendar sync.
• Google Docs Documents, spreadsheets, and presentations.
• Google Groups User-created groups providing mailing lists, easy content sharing, searchable archives.
• Google Sites Secure, coding-free web pages for intranets and team managed sites.
• Google Video Private, secure, hosted video sharing.

Gmail for Business is a mature Enterprise ready product, Docs is maturing and Sites is not yet a Sharepoint alternative.  However, the Google Development teams are moving quickly.   There are also a growing number of complimentary third party add on solutions.