During the 2015 Blender Conference (from 23 to 25 October) many products at BlenderMarket will come with a 20% discount. Of course I will participate in that sale as well, so if you were thinking about purchasing either WeightLifter or Space Tree Pro, now is your chance to get an even better deal :-)
Now I wouldn't want to exclude my Open Shading Language for Blender E-book from the fun so even though it is not marketed by BlenderMarket it will carry the same 20% discount during the Blender conference. Get it on Smashwords and enter the coupon code
EY53W on checkout.