Your best bet is to go with VirtualBox.
If you are new to virtualization it shouldn't be too difficult, but just in case:
- Click "New" (Badge looking Icon)
- Give it a name, select "Linux" and under that select "Ubuntu" or "Ubuntu (64-bit)" and click "Next"
- Allocate the amount of memory you are willing to dedicate to the guests (make sure you leave enough for the host machine) and click "Next"
- Select "create a new virtual hard drive now" and click "Next"
- Select "VDI" and click "Next"
- Select "Dynamically allocated" and click "Next"
- Give it a name, select the maximum size, and click "Next"
- You should now be out of the wizard. Select the machine you just created and click "Settings" (looks like a gear)
- Under the Storage tab, click on "Controller: IDE" and click the little DVD, and select "Choose Disk"
- Find your .iso of choice and click open.
- Click "Okay" and you should be set.
- Select the machine and click "Start"
- Install Ubuntu like you normally would.
- Rinse and repeat! (or you can right click on the machine and select "Clone")
Hope this helps!