Frogg Toggs seemed loud in the store if memory serves. I'm sure they keep you dry as a bone, but they just struck me as too "crunchy". What do you think?Not going to keep you warm by no means but as far as packability and keeping you dry to boot, you cannot beat the frogg toggs in my opinion. You can rool them up into a ball not much bigger than a ball cap.
+1cabelas space rain gear packs the smallest i've seen.
Pricey, but worth it...