For very lightweight travel, and decent waterproofness, Montanes Freeflow Velo H2O jacket.
Its a basic Pertex jacket, but for the price of around £60, its excellent, and weighs very little, and packs away into a stuff sack that's the size of an Apple.
Its hood is the best ive ever used, fully adjustable, and gives superb protection.
For those warmer summer months, its worth a look.