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

$ glue source output

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

• Automatic Sprite(PNG+CSS) creation.
• Supports multi sprite projects.
• Automatically crop unnecessary transparent borders around the source images.
• Configurable paddings per image, sprite or project.
• Generate .less files.
• Automatically post-process sprite images using OptiPNG.
• Read configuration from static config files.
• Configurable cache busting for sprite images.

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

And also a 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:https://glue.readthedocs.org/en/latest/quickstart.html