JSoko is a Java program for playing the Sokoban game.
It's developed as an open source program at www.sourceforge.net
Current version of JSoko is 1.99
Ken'ichiro Takahashi (Takaken) has published "Sokoban Minimum Moves Solver Version 1.2",
a solver searching for minimum moves solutions.
It can process levels having at most 8 boxes.
Moreover, the last 20 moves are not displayed after solved, according to the website.
You can find more information and even the source code of this solver at his website.