On July 4, the developers announced a new release of MegaMekLab version 0.1.29. While the new version does not squash a lot of bugs (just 5) it has been altered to work better with the latest stable version of MegaMek.
MegaMekLab is a java-based freeware program that allows you to build various units, such as BattleMechs, Infantry and Vehicles, and those can be transferred to MegaMek. Add your favorite designs to the latest stable version of MegaMek. And get your Mek on!