Sea To Summit has some of my favorite options for keeping your backpack dry while traveling. Depending on where you travel, the season you travel, and what activity your doing, you may very well have a need for staying dry when it rains. And backpack covers or liners are a great option for not having to worry about the elements. The picture above is Sea To Summit’s line of lightweight dry bags. The are designed to fit inside your backpack or really anything your need to squish it in. They make a heavier dry bag, however this is good for tight spots. Imagine your camera and railpass getting wet, and you will see why this is a necessity for backpackers and travelers.