Figured I'd leave my vote for Redreader here. It's open source, works offline (has a fully featured cached versions system) and I've used it for years. It also

Figured I'd leave my vote for Redreader here. It's open source, works offline (has a fully featured cached versions system) and I've used it for years. It also supports custom tabs too, so if you use a decent browser with add-on support (Firefox) you can get ad-blocking working for all articles you read within the app. https://github.com/QuantumBadger/RedReader/ https://github.com/QuantumBadger/RedReader/