There are few places online where you can do an overview of the system and try the different available apps.
Also the latest version of Odoo Enterprise is available at https://demo.odoo.com/ where a new database is created for temporary use and later removed. So next time when you visit the website a new database will be created, which means all your previous changes will not be available.
Another website where can be experienced different versions and editions of Odoo is https://runbot.odoo.com/. This environment offers all supported versions and the two different editions. However, since this is managed by Odoo only the official Odoo apps are available. The credentials for logging to any of these databases are admin/admin. Additionally, it is worth mentioning that these databases are available worldwide so all changes done in them are available for everyone.