Thanks to @DougChasman we have learned here that both ToolingAPI and MetadataAPI are fully supporting AuraDefinitionBundel and AuraDefinition right now as BETA and we can start to use them.
Doug also provided links to the MetadataAPI documentation, which helped me a lot to implement it into CodeFusion using MetadataAPI.
Now I would be very interested, if there is also a bit of documentation about Aura regarding ToolingAPI. As with other Metadata-Types, I'd like to support both APIs switchable, wherever possible.
Or has anyone already saved an AuraDefinition as single File via ToolingAPI? I would prefer not to deploy the entire Bundle but only save e. g. MyAppController.js - is that possible?
Probably I could answer most of my questions to myself by looking at Dave's https://github.com/heroku/force - but if anyone already used ToolingAPI for Aura deployment, any insights would be appreciated.