Fluid and Extbase are cool stuff! Really. Right now I create a new extension for a Namics customer and I am also working on a port of my podcast extension. All the basic stuff is already done; creating xml, rendering views for the podcasts including HTML5 Audio output etc. – if you like to offer help, leave me a comment.
One thing I found laking was, that objects assigned to the view are html encoded – this means, that if you assign the view a prerendered tag, lets say a captcha-image, it will show up as text and not as html tag. There is no easy way around it – that said, if you’re not up to abuse the helper by providing a wrong parseFuncTSPath argument. That’s why I have written two simple fluid view helpers that might help you with your own extension:

htmlDecode View Helper

class Tx_YourExtensionKey_Format_HtmlDecodeViewHelper extends Tx_Fluid_Core_ViewHelper_AbstractViewHelper {
    /**
     * Decodes a given string to HTML
     *
     * @param string $string the string to be decoded
     * @param string $quote_style The optional second quote_style parameter lets you define what will be done with 'single' and "double" quotes. It takes on one of three constants with the default being ENT_COMPAT:
     * @param string $charset The URF-8 character set is used as default for the optional third charset. This defines the character set used in conversion.
     * @return string htmldecoded string
     * @author Noel Bossart
     */
    public function render($code = NULL, $quote_style = ENT_COMPAT, $charset = 'UTF-8') {
        if ($code === NULL) {
            $code = $this->renderChildren();
        }
        return html_entity_decode($code, $quote_style, $charset);
    }
}

htmlEncode View Helper:

class Tx_YourExtensionKey_ViewHelpers_Format_HtmlEncodeViewHelper extends Tx_Fluid_Core_ViewHelper_AbstractViewHelper {

    /**
     * HTML encodes a given string
     *
     * @param string $string the string to be encoded
     * @param string $quote_style The optional second quote_style parameter lets you define what will be done with 'single' and "double" quotes. It takes on one of three constants with the default being ENT_COMPAT:
     * @param string $charset The URF-8 character set is used as default for the optional third charset. This defines the character set used in conversion.
     * @return string HTML encoded string
     * @author Noel Bossart
     */
    public function render($code = NULL, $quote_style = ENT_COMPAT, $charset = 'UTF-8') {
        if ($code === NULL) {
            $code = $this->renderChildren();
        }
        return htmlspecialchars($code, $quote_style, $charset);
    }
}

You can download both view helpers and put the files into the following folder: EXT:/yourextension/Classes/ViewHelpers/Format/

Updated: Or you just use html_entity_decode() before you pass it to the view :)