- Itty Bitty Labs — creators of Reveal
- NSHipster — highlighting different, sometimes obscure, parts of Cocoa, Cocoa Touch, Foundation, and more
- objc.io — A monthly-ish periodical of Objective-C / Cocoa / Cocoa Touch development; one of the best
- Peter Steinberger — he's a young curmudgeon, a grudgeful iOS developer; an excellent counterpoint to all the iOS/OS X love letters, with decent common sense
- Use Your Loaf — quasi-frequent (every other week, now?) iOS development tips
- iOS Dev Weekly*— a weekly digest of great iOS development articles; I get these via email
- Ray Wenderlich — mostly tutorials, but many of them catch my eye as they pop up in my RSS feed
- Ole Begemann — more general Apple developer culture and things
Actually, Ole Begemann has another great list of other blogs.