User Activity

Team,  I currenlty own a 70D and a T3i with a bunch of EF-s lenses. My question is wether to upgrade to a couple of L lenses or upgrade to a full frame camera.  Ideally I love to have a Mark III but a 6D is more realistic.   My budget is about $3500 ...
Does anyone have a great Canon shutter speed online tutorial you would like to share?
Does anyone have some good reference/reading material that you can share with me, I would like to experiement with filters. Ive googled some stuff but did not find strong material.  Any help on this would be greatly appreciated. 
Team, I recently purchased a Sigma 17-70mm F2.8-4 DC Macro and would like to hear from you guys abotu other lenses out there that are excpetional as well.  So far i have nothing but good reviews for this lens.  Im new to the Sigma brand.  thanks, 
can anyone send me to a website or service that has decent deals?