Is there a way to select sibling nodes?

Well... sure... just access the parent and then the children.

 node.parentNode.childNodes[]

or... using jQuery:

$('#innerId').siblings()

Edit: Cletus as always is inspiring. I dug further. This is how jQuery gets siblings essentially:

function getChildren(n, skipMe){
    var r = [];
    for ( ; n; n = n.nextSibling ) 
       if ( n.nodeType == 1 && n != skipMe)
          r.push( n );        
    return r;
};

function getSiblings(n) {
    return getChildren(n.parentNode.firstChild, n);
}

var sibling = node.nextSibling;

This will return the sibling immediately after it, or null no more siblings are available. Likewise, you can use previousSibling.

[Edit] On second thought, this will not give the next div tag, but the whitespace after the node. Better seems to be

var sibling = node.nextElementSibling;

There also exists a previousElementSibling.