Glue is a simple command line tool to generate CSS sprites:

$ glue source output

• The latest documentation is available at: http://glue.readthedocs.org
• Installation instructions: http://glue.readthedocs.org/en/latest/installation.html

• Automatic Sprite (PNG+CSS) creation.
• Support for multi-sprite projects.
• Multiple algorithms available.
• Automatic crop of unnecessary transparent borders around source images.
• Configurable paddings per image, sprite or project.
• Optional .less output format.
• Automatic sprite images post-processing using OptiPNG.
• Sprite- and Project-level configuration via static config files.
• Configurable cache busting for sprite images.
• Customizable output css templates.
• Customizable CSS class names.

Using the gorgeous famfamfam icons (4.2Mb) you will get the following icons.png (401Kb).

And also an icons.css with all the necessary CSS classes for this sprite:

.sprite-icons-zoom_out{ background:url('icons.png'); top:0; left:0; no-repeat;}
.sprite-icons-zoom_in{ background:url('icons.png'); top:0; left:-16; no-repeat;}
.sprite-icons-zoom{ background:url('icons.png'); top:-16; left:0; no-repeat;}
.sprite-icons-xhtml_valid{ background:url('icons.png'); top:-16; left:-16; no-repeat;}
...

Do you want to know more? Visit the quickstart guide: http://glue.readthedocs.org/en/latest/quickstart.html