KDE has released the second beta of the 4.13 versions of Applications and
Development Platform. With API, dependency and feature freezes in place, the
focus is now on fixing bugs and further polishing. Your assistance is
requested [1].

A partial list of improvements can be found in the 4.13 Feature Plan [2]. A
more complete list of the improvements and changes will be available for the
final release in the middle of April.

This second beta release needs a thorough testing in order to improve quality
and user experience. A variety of actual users is essential to maintaining
high KDE quality, because developers cannot possibly test every configuration.
User assistance helps find bugs early so they can be squashed before the
final release. Please join the 4.13 team's release effort by installing the
beta and reporting any bugs [3].

The official announcement [4] has information about how to install the betas.

[1] http://dot.kde.org/2014/03/12/applications-413-coming-soon-help-us-test
[2] http://techbase.kde.org/Schedules/KDE4/4.13_Feature_Plan
[3] http://bugs.kde.org
[4] http://www.kde.org/announcements/announce-4.13-beta2.php