html5-preloader
JSL
LABjs
yepnope.js
head.js
ControlJS
load.js
$script.js
lazyload
DeferJS - Contains also a jQuery specific version.
jQI
YUI 3: Get
dominatejs
bootstrap
StealJS
DominateJS
BravoJS
NBL.js
Hydra.js
includejs
yuno
wreq
These libraries conform to the AMD module definition.
RequireJS
curl
loader-js
bdLoad
almond - A minimal AMD API implementation for use after optimized builds.
JavaScript Loader Comparison (Google Doc Document)
Reddit - How do you guys build your js files for deployment?