But wouldn't it be convenient if you could access and manage those other applications from within Google Apps (if only to avoid password proliferation) and enjoy tighter integration to eliminate the need to copy and paste data between different providers' applications?
That's now possible with the launch of Google Apps Marketplace.
"The Google Apps Marketplace allows Google Apps customers to easily discover, deploy and manage cloud applications that integrate with Google Apps," said Chris Vander Mey, product manager, Google Apps Marketplace.
Only administrators can add an application to a domain, and it is up to the administrator to authorise the new application to access data stored in Google Apps.
"More than 50 companies are now selling applications across a range of businesses," said Vander Mey.
Applications that have received a strong reception from early users include Manymoon (task and project management; uses Calendar, Contacts, Docs, and Spreadsheets), Socialwok (collaboration and project management; uses Calendar, Contacts, Docs, Sites, and Spreadsheets), and Cordys Process Factory (workflows involving Google Apps).
Zoho has been presenting its range of cloud applications as an adjunct - and in some cases an alternative - to Google Apps. For example, it has been possible to attach a Google Docs document to Zoho Projects' Documents module.
The company now offers Zoho CRM (CRM; uses Calendar, Contacts, Docs, and Spreadsheets) and Zoho Projects (project management; uses Calendar, Docs, and Spreadsheets) through the Google Apps Marketplace.
Perhaps the biggest name to join the Google Apps Marketplace is Intuit, which offers Intuit Online Payroll for Google Apps. This apparently US-specific application handles payroll processing including cheque printing and filing taxes. Employees can view their pay stubs from Calendar.