Mojang has been released version 1.7.7 with an important bugfix to fix some server crashes. This version contains some bugfixes, a few updates to make Realms even better than it already is and prepares Minecraft for the renaming feature that will eventually allow you to rename your player. The renaming feature will not be available right now, but this is an important step towards it. We have also changed the internal handling of player skins to make use of our new, improved skin servers.
Because this is important, let me repeat that last sentence: Please make sure that you are in the correct server mode (online mode/offline mode) when you start the 1.7.7 server for the first time, because profiles are not compatible between these two server modes.
Cross-platform server jar: https://s3.amazonaws.com/Minecraft.Download/versions/1.7.7/minecraft_server.1.7.7.jar
Cross-platform server for windows (exe): https://s3.amazonaws.com/Minecraft.Download/versions/1.7.7/minecraft_server.1.7.7.exe
Credits: Mojang Team