Below are some of websites and blogs I have found useful and visit regularly. Feel free to recommend your own favorites.
New York City
Brownstoner > news & commentaries about Brooklyn real estate
Curbed > news & commentaries about new york city neighborhoods and real estate; often humorous
Performing Arts
Concert Hall: Carnegie Hall • Lincoln Center for the Performing Arts
Orchestra: New York Philharmonic • Wiener Philharmoniker • Berliner Philharmoniker
Ballet: American Ballet Theatre • New York City Ballet
Opera: The Metroplitan Opera • Teatro alla Scala
Politics
The Daily Dish > commentaries by Mr. Andrew Sullivan
The Institute of Politics > at the John F. Kennedy School of Government, Harvard University
Politico > news & commentaries
Real Clear Politics > data & commentaries from multiple sources
Rush Limbaugh > transcripts from Mr. Limbaugh’s radio program
Religion: Christianity
Bible Gateway > online Bible site; particularly useful for searching in multiple versions and languages
Desiring God > ministry of John Piper
Westminster Bookstore > affiliated with Westminster Theological Seminary
Church: Christ Church United Methodist • Redeemer Presbyterian Church • Saint Bartholomew’s Church • Saint Thomas Church
Technology
AppleInsider > news, rumors & commentaries about Apple and related products
The Boy Genius Report > news, rumors & commentaries; emphasis on mobile tech
Engadget > news, rumors & commentaries
RIMarkable > news, rumors & commentaries on Research In Motion’s BlackBerry
Slashdot > general technology news; more technical
TidBITS > news & longer articles about Apple and related products