Unstable releases
From smplayer
Here you can find the very latest versions of smplayer. They can have improvements and bugfixes but they can also be a little bit more unstable.
There are several packages available. Usually you would download the more recent one. In case you find an important problem on it, you can try an older one.
Source Packages:
Read the file Install.txt included in the package to know how to compile.
Windows Packages:
Update for Windows. Installation: Uncompress the package on the same directory where you installed SMPlayer, overwriting the old files. 7z files can be opened with 7-Zip.
Packages for Ubuntu:
You can install these packages with sudo dpkg -i package.deb
