The Extended Editions of all three The Lord of the Rings films will be released in theaters and on Blu-ray in June.  The Extended Editions, originally released on DVD in 2004, added 30 minutes to Return of the King, 43 minutes to The Two Towers, and 50 minutes to Return of the King
The new box set will included six Blu-ray discs (two for each movie) and nine DVDs for the extras, all at an MSRP of $119.90.   
The theatrical release will show each Lord of the Rings Extended Edition on one night over three weeks:
June 14:  The Lord of the Rings: The Fellowship of the Ring
June 21:  The Lord of the Rings: The Two Towers
June 28:  The Lord of the Rings: The Return of the King
Each showing will be preceded by an introduction from director Peter Jackson, from the set of The Hobbit in New Zealand.  Showings will kick off at 7 p.m. local time. Around 450 theaters have been announced as participating in the showings to date.
The Blu-ray/DVD set releases June 28th.