it's pretty easy. you just make a form using html and have a script send the email....i usually use php to send the email, but you could use perl (.cgi) as well. the form would be like
Code:
<form action="http://thescript" method="post">
<input type="text" name="yourname">
<input type="text" name="email">
<textarea name="comment"></textarea>
<input type="submit" value="send it">
</form>