Since you are using a map your itteration is based on keys within that Map. So the basic syntax looks like this:
<g:each in=${yourCoolMap.entrySet()}" var="entry">
${entry.key} = ${entry.value}
</g:each>
Thus, your code will look something like this:
<g:each var="myList" in="${statusMap.entrySet()}">
<div id="pending_list" class="onTop">
<g:render template="/list" model="['list': myList.value, 'listSize': myList.value.size()]" />
</div>
</g:each>