A way to extract layer sets from PSD files without Photoshop?
The easiest solution might be to download the Photoshop trial version from Adobe.
ImageMagick supports PSD layers and can extract them to separate image files. But I like Joe Internet's answer if you only have to do this once or twice.
GIMP does read the layers (I use GIMP 2.6 sometimes) altough it doesn't understand layer properties made in photoshop (like borders and shadows) or folders (groupings) which are made in photoshop.
Paint Shop Pro opens PSD files too