Is there any website that allows me to try joomla, or drupal online?
Basically I want to learn Joomla and Drupal, but don't feel like download the whole source and install it on my computer and start configuring it. I would prefer an online service ( preferably free!) that allows me to do just that.
Is there any such websites available?
The individual websites for each usually have a demo!
Joomla: http://demo.joomla.org/ Drupal: http://php.opensourcecms.com/scripts/details.php?scriptid=191
Opensourcecms.com has many CMS's on it also, and most have links to their demos.
One handy way to quickly try various web apps is to use a pre-built virtual machine. Here's one place to get them:
http://www.vmware.com/appliances/directory/cat/502
Simply download the VM and start it up. Each one is a fully configured system with the application already installed. You can work with Drupal, Joomla, WordPress, and many more. When you're done trying it out or if you want to start fresh, just throw it a way and grab a new one.
Once you get a hang for something through the VM, though, it's definitely worth taking the time to practice installing and configuring it.