Decentralized microblogging using Sone, the twitter-like system on Freenet. Freemail, the encrypted email system. FMS, the forums. I also use the distributed data store for storing data. Basically anything you'd use IPFS for but more anonymity.

Here's an example of using it for the backing store for my blog: https://bluishcoder.co.nz/2015/09/14/using-freenet-for-stati...

Here's a series of articles on writing dynamic apps for Freenet - in this case chat-like things http://www.draketo.de/light/english/freenet/communication-pr...