Results will vary depending on your machine but it may be quicker to burn and reboot to testdrive a LiveCD. If you want to try VirtualBox though, this is how you do it.
I decided to take a look at Fedora 11 and I thought that if I wanted to take a look at other LiveCDs in the future may as well set up VirtualBox and save myself the time of burning and restarting to take the look at them. Virtualbox is a bit slow but not terribly though. Note: I don’t have virtualization on my CPU though so load-times may alot better with it.
Virtualbox has been getting some good reviews and is easy to use. Locate you distro’s documentation and find out how to do this.
Once Virtualbox has been installed load the module:
sudo modprobe vboxdrv
VirtualBox in the KDE menu is under System > Sun VirtualBox, or you can just type
VirtualBox in a terminal.
Click New in the VirtualBox window, name it, select OS type and version. Select base memory size as 512MB (most operating systems will need at least 512MB to function properly).
To create a hard disk image, when the new image has been created click Settings then CD/DVD-ROM and check Mount CD/DVD Drive, and then add the ISO image.
In the General dialogue select the Advance tab and check Enable IO APIC.
That’s it. You should now be able to load a LiveCD from VirtualBox.
I wrote a post on top of this about creating you own LiveUSB: