Newsstand, one of the slickest RSS Readers in the app store just released a new version (2.1) that allows saving to Read It Later.
Newsstand provides sync with Google Reader, an integrated feed directory of popular blogs and websites, and a very easy to use interface.
Download: Newsstand 1.2
Newsstand’s ability to save to Read It Later is provided by the Read It Later Open API which lets any developer add RIL support to their applications.