Add to Ironraven's list, the first aid kit.

My kits are all in groups and all within separate 6 mil zip-locks available in various sizes through www.royalbag.com . Not only do the zip-locks keep items dry, they also keep items sorted into groups. FAK, fire starting, food gathering, tools, water treatment, directional and signaling, etc. IMHO heavy zip-locks are a very convenient and efficient way to keep small to medium size kits of any type well organized and dry.