Here is a list of the contact emails for sending a DCMA to the most common file share sites:

Hotfile - abuse@hotfile.com
RapidShare - abuse@rapidshare.com
Letitbit - abuse@letitbit.net
Unibytes - abuse@unibytes.com
Megashare - abuse@megashare.com
Megashares - abuse@megashares.com
Easy-Share - abuse@easy-share.com
Filesmonster - abuse@filesmonster.com
Filesonic - abuse@sharingmatrix.com, dmca@sharingmatrix.com
Imagehost - abuse@imagehost.org
Imagebam - abuse@imagebam.com
Gigasize - abuse@gigasize.com
SMS4file - abuse@sms4file.com
Vip-file - abuse@vip-file.com
Loshare - abuse@loshare.com
Storage.to - abuse@storage.to
Fileserve - dmca@fileserve.com
Filefactory - dmca@filefactory.com
Sendspace - dmca-agent@sendspace.com
Wordpress - dmca@automattic.com
Furk - dmca@furk.net
Filestube - dmca@filestube.com
Rmtinfo - dmca@rmtinfo.com
Imagebam - dmca@imagebam.com
Imageevent - copyright@imageevent.com
Yahoo - copyright@yahoo-inc.com
Oron - support@oron.com
Fastpic.ru - info@fastpic.ru
Kewlshare - contactus@9kewlml.com
Zakachkafile.com - stimulprofit@gmail.com
Super-filezz - files4cash.support@gmail.com
Uploaded.to - support@uploaded.to

Please feel free to add any others that I missed.