Earlier we have wrote about the CSS sprites and how to increase the speed of your website loading using CSS sprites here How to increase Speed of Your Website for better Page Rank – SEO – Part I Css Sprites. Using CSS sprites you are reducing the number of http requests and thus increasing the speed of the website.
There we have described about a free online CSS Sprites generator http://csssprites.com/
Here comes few more
You can read a post on Shout Me Loud here on these CSS sprite generators