You can run ubuntu from Bootcamp or Paralells. My son does it on his Mac

Yes, you can run Linux in virtual, such as Parallels oreven VMWare , and you can
dual-boot as well.I run a dual-boot with MacBook Snow Leopard 10.6.
I used Boot camp to carve out a 50 gig partitionand also used (must download it
I think) rEFIt boot managerthat lets me pick between OS-X and Linux at startup.
Doing the entire process was really easy. Â The hardest thingabout it (that is--
what you must be careful, really careful) isdo not install GRUB on the MBR,
install it on the Linux partition.
Here is a simple tutorial that made it a breeze for me.
www.maclife.com/.../install_linux_your_mac

I really like VMWare Fusion, it has worked great and I current have
Ubuntu 9.10 x64 with 4g of ram. It runs fast on the MAC and so does my
other operating system, so fast that I have less trouble running them on
OSX.. No blue screens...

There is also Virtualbox for the Mac.