Rucksack
Rucksack is a jquery plugin to arrange elements that can fit in the given width. It relies on the knapsack algorithm.
Usage:
$('#container').rucksack({
  width: 'width to fit in. defaults to 960px',
  class: 'class name to be given to the div that will contain the elements of one row. defaults to rucksack'
})
Example
Here's a working example by @omgmog
Another example by ctcherry