I've been using different loaders in the past, here are the most popular:
bulkloader by arthur debert: https://github.com/arthur-debert/BulkLoader
loadermax by greensock: http://www.greensock.com/loadermax/
queueloader by hydrotic: https://github.com/hydrotik/QueueLoader/wiki/
Which one is the best one and for which challenges?
Loadermax has a smaller filesize than bulkloader and has a lot of nice extras like for example nest loaders in each other).
It's sort of a bulkloader on steroids. You should check out it's features @ http://www.greensock.com/loadermax/
I've been using bulkloader for a few years now, and it's very good, though loadermax is just that little extra that's worth your while (and can be as small as 7k)...
(I don't know about queue-loader though)