NetNewsWire 5.0 was just released as open source. Ever since Google Reader shut down, I've been using Feedly as an aggregator and Reeder for iOS. Reeder makes it very easy to import Feedly feeds but it isn't as straight forward for NetNewsWire. Fortunately, Feedly and NetNewsWire both support OPML (Outline Processor Markup Language) to import/export feeds. Feedly buries this so here's a quick step-by-step to get up and running with NetNewsWire and Feedly.
Sign in to Feedly and click the gear.
From the settings, next to the import OPML click and the export button.
From NetNewsWire, select File -> Import Subscriptions and import your OPML file
That's it! Enjoy. I highly recommend Reeder for iOS.