Insert a node field programmatically
You can put php code in a block template and write something like:

$node = node_load($node_id);


and then access the specific field you want to show like:

print $node-&gt;title;
print $node-&gt;field_yourfield["und"][0]["value"]


Edit:

Also, you can modify the node template for the teaser, copying the node.tpl.php file in your subtheme (you can look how to make a subtheme here) and putting the html structure you want inside:

if($teaser)
{
...
}


There are other displays available for nodes other than page and teaser.