With currently five OSes installed on my 100GB hard drive, I can confirm that it is indeed possible to have more than a dual-boot.
You'll have to take some space from either Ubuntu or Windows to install kali.
I won't elaborate much, since it's explained well in the kali linux documentation: http://docs.kali.org/installation/dual-boot-kali-with-windows
As a side note, kali will install a new bootloader, which will replace Ubuntu's. While this isn't nessecarily bad, if you want ubuntu's classy purple GRUB, you may want to look up how to use
Just a hint: search. There's a lot of documentation out there.