Packing Light

I've become a fairly experienced traveler, but I'm always open to new ideas for traveling smart and efficiently. It's probably safe to say that every traveler has their own unique experience with the places they visit and the people they meet along the way. Though I'd love to hear your stories and philosophies on traveling, what I'm hoping will accumulate on this page is a collection of useful items I wouldn't want to be without on my travels. Keep in mind that I'm trying to pack light--as in, one bag and that's it!

At the moment, the top items on my list are:
~REI's Grand Tour 85 traveler's backpack
~passport
~international driver's license
~money pouch (for credit/debit card, cash, passport/ID)
~Asus TF300 tablet
~HTC One X smart phone
~Canon PowerShot SX230 HS digital camera
~power adapters (1 for UK, 1 for continental Europe, 1 for Italy)
~mini power strip (3 outlets + USB)
~locks (4 for backpack, 1 for hostel lockers)
~jacket (1)
~sweater (1)
~jeans (2)
~shorts (2)
~running/walking shoes
~evening/dress shoes
~workout clothes
~swimsuit
~sunglasses

~sandals

I can always purchase things once I get to where I'm going, but certain items like the ones above will be helpful to have on hand from the get-go. Let me know what I've forgotten!