Nothing fancy but functional for Web Development.
Default parameters:
width: 1px; height: 1px; color: #FFFFFF; text: none; type: png
http://joachimfraatz.de/images/generator
White GIF
http://joachimfraatz.de/images/generator/100x100.gif
PNG with alpha
http://joachimfraatz.de/images/generator/200x100/00ccff79
PNG with alpha and printed dimensions
http://joachimfraatz.de/images/generator/200x100/00ccffcc/
GIF with custom text
http://joachimfraatz.de/images/generator/200x100/00ccff/Hello World.gif
You have to configure mod_rewrite with the contained .htaccess file or the Apatche config to use the path syntax. Otherwise use GET vars (width, height, color, text, type)
Just download the image generator and run it on you local server!