This is a great list of ways to curate content. Most of them also have apps. Diigo and PearlTrees work well on iPad. Flipboard is another great option.
This claims to be the first browser created by a doctor that is just for kids. The idea is that parents and educators curate content and students then can only access what they have identified. An interesting concept to present curated vs. filtered content.
With Pocket, it's possible to curate content to read offline or online. It has similar features as Diigo, but uses a visual interface similar to Flipboard. Definite potential here.