Janetter - Janetter is a Twitter client application. Faster, smarter, and more powerful.
Mobbin - Latest mobile design patterns & elements library
YoruFukurou - YoruFukurou (NightOwl) is a Twitter client for Mac OS X, designed for Twitter addicts.
pttrns - iPhone and iPad user interface patterns
Talon for Twitter - Elegantly designed, ad-free Twitter experience for Android
Page Flows - User flow design inspiration for mobile & desktop