Hi
I would like to build a website similar to "www.cooltext.com" and
"www.flamingtext.com". I understand that they are using GIMP but I
wonder how I put the logo or text rendering machine on my site so that
people could generate logos or specail text effects online without
having to download GIMP. Basically I want to build same as
cooltext.com. I think they are using javascripts but as I said I like
to know which software or scripts I could use. Please tell me where I
could download such scripts?

You have two options, create your own online graphic tool using a
library similar to GD or you can simple use a frame or iframe in you
web pointing to www.cooltext.com.

Maybe this book will help you:
http://www.amazon.com/Programming-Graphics-Software-OReilly-Nutshell/dp/1565924789

You can control GIMP from the web with Perl.
Try a google search for mor information:
://www.google.com/search?num=50&hl=en&lr=&safe=off&q=gimp+perl+&btnG=Search

i am writing this script. You can show it
http://www.uzatma.be/yaziyapistir/yaziyapistir.php