According to Neowing, the DVD & Blu-ray volume 1 limited editions of "Toaru Kagaku no Railgun
" will include an extra short anime. It will be released on January 29th, 2010. Short novel episodes of "Toaru Majutsu no Index
" will also be bundled with the limited editions of the eight volumes. The episodes are called "Kanzaki Kaori chapter".
Updated on April 14th
According to the official website, the DVD & Blu-ray volume 5 will include another extra anime. It will be released on May 28th.
]Railgun official website[/url]