You sure can.
LILO and
GRUB are the two Linux bootloaders that allow you to choose from multiple OSs to boot from. I don't know which one is the default for Ubuntu. GRUB is a bit nicer looking. I guess I'm just a bit more familiar with LILO, so that's what I use with Slackware.
You need to create a separate partition for each operating system that will be installed. I usually install Windows first. Then, after installing Linux, depending on the distro, you may be asked to configure the bootloader with any additional, non-Linux OSs you want to be able to boot from.
The exact procedure is going to be a bit different depending on which OSs you install, which Linux distro, which bootloader, etc, but that's the general idea.