Most interesting free and opensource software of December:
Freemake Youtube to MP3 Boom is Youtube video to MP3 converter for Windows, easy to use, allows to listen preview, download in high quality
TakeOwnershipPro Windows utility that allows to make any task on files and folders by granting full permissions (eg. when a file cannot be deleted)
Pricepirates search the best offers in various marketplace for a given product, for Windows
DiskBoss is a good Windows hard drive management tool
SSL Enforcer for any browser or app, check for secure alternatives connections (HTTPS) and perform automatically redirect. Available for Windows and Mac OS X