Depending on the CPU you are using, be careful regarding the voltage required for the Memory, it might be more prudent to keep the voltage requirements down if your looking to use 4+ modules, otherwise you may suffer memory controller issues resulting in instability.
Mushkin is a well know and well respected brand, and produces some very good RAM, which only require 1.5v rather than the more common 1.65, they also do a super low voltage module that needs only 1.35v
Patriot also make low voltage DDR3 modules (1.5v in their G series aimed at AMD users) and are a good quality brand, i would have no problem recommending them, a lot of their current range however need 1.65-1.7v