After only three years, the L Magazine’s Northside Festival has already become a North Brooklyn institution. The annual event brings together dozens of bands and packs out a number of venues in Williamsburg and Greenpoint for four days of musical ecstasy, starting on Thursday. There’s something there for everyone, but highlights include the opening night party at the Music Hall of Williamsburg, featuring much-buzzed-about artist Theophilus London (UPDATE: advance tickets are sold out, as are badges); Thursday’s performance at Bar Matchless by the endearingly acoustic Eamon Hamilton, of UK band Brakes; Friday’s sold-out show with Beirut and Sharon Van Etten; PopGun’s showcases at Glasslands on Friday and Sunday; Guided by Voices with Wavves and Surfer Blood on Saturday (for which tickets are still available); the Fiery Furnaces’ Eleanor Friedberger at St. Cecilia’s Church on Saturday; and Deer Tick performing as the Nirvana-covering “Deervana” on Sunday — advance tickets are sold out, but they’ll be selling tickets at the door for $15 (cash only) starting at 6pm. The Northside Festival isn’t just about music, though; they’re bringing back their Northside Film screening series at indieScreen, and will also be incorporating art shows, as well as tech-y panels under the banner of “Northside Ideas” (not unlike a mini-SXSW Interactive). For schedules and details on all of this week’s happenings, visit the Northside Festival’s website.