Want to download all sessions of #MSIgnite 2015 easily? Simply use this PowerShell script which was originally published at https://gist.github.com/nzthiago/5736907.
I improved it and customized it for MSIgnite 2015 so that also slides are downloaded, to use absolute path and no directories and counting, fixing special filename chars and wait for a key at the end.
Download Ignite15Videoandslides.zip
Another script is available at Channel9 Session Downloader v1.81 by Michel de Rooij.
Enjoy the (downloaded) sessions!