I've quickly knocked up the following:
html code:
<script type="text/javascript">
function add_input(){
document.getElementById('input_container').innerHTML += '<input type="text"><br />';
}
</script>
<div>
<form>
<div id="input_container">
<input type="text"><br />
</div>
<br /><input type="submit" value="submit">
</form>
<a href="#" onclick="add_input()">add input</a>
</div>
...which just adds a form input when you click the add input link. However, I want to be able to retain the information pre-entered in the inputs, so if I typed something into the first input, click add another, and I would have whatever I typed in the first plus another input (currently it just replaces the div contents with a new set of inputs). Any ideas?