Ubuntu 15.04 - released in April 2015 and supported until January 2016.
There's also Ubuntu 14.04, the latest LTS release. It was released in April, 2014, and will have support until April, 2019.
Canonical cranks out a release every 6 months. Non-LTS releases receive support for 9 months, while LTS releases (released every two years; receive support for 5 years. The version scheme is year.month, so the next Ubuntu release due in October will be 15.10. The next LTS release will be 16.04, next April.
You can also go to distrowatch.com to track the latest releases and package versions of various distros, and Ubuntu.com has tons of documentation with this information and more of this type.
Last edited by wagscat123; 08-04-2015 at 04:59 PM.