Hiya,
The easiest way to do this IMHO is with a javascript document.write in an external ".js" file. A ".js" file is called by a "<script src=yourscript.js>" and closed with "</script>" just like a normal script. The .js file itself is plain text and can be used to simply output text (or html) to be written dynamically to a page when used with the javascript document.write function.
You can find this script easily anywhere on the web.
A simple .js file to write some plain text to a page:
CODE
<!-- document.write("
Put your text, form, html-markup for image, links, etc. in here, but no matched parentheses! We do NOT want to close our script early...
") //-->
PLEASE don't use flash unneccessarily, some (the majority, possibly) of users are still on dialup...