With css3 support you could do this:
.container {
-moz-column-count: 2;
-moz-column-gap: 10px;
-webkit-column-count: 2;
-webkit-column-gap: 10px;
column-count: 2;
column-gap: 10px;
width: 360px;
}
.container div {
display: inline-block;
width: 100%;
background-color: red;
}
With no css3 support, you have to resort to js unfortunately.