With the release of the Raspberry Pi 2 Model B and its ARM Cortex-A7 CPU, users are offered a number of ways of running Ubuntu.
If you like being at the cutting edge, you may be interested in trying an image of Vivid Vervet, the code name for Ubuntu 15.04. This is a development release, as Ubuntu 15.04 is not scheduled for release until next month. It offers a number of interesting features and improvements.