The Ultimate Female Packing List. She has a list for most regions and seasons--leaning heavily toward backpacking-style travel--plus plenty of tips on products that will make your trip a little easier.
How To Pack 2 Weeks In A Carry-On (really good packing/travel tips)
Clean out an old lotion bottle and use it to hide your phone, ID, credit cards, money, & keys in your beach bag.
Easy cover-ups for magazines, books, phones, and more. (Wish I'd had one for my book in Hawaii!)
Mini roll-up travel charger for iPhone/iPad, iPod, and Droid. $49 (Available from Restoration Hardware. Idea via @ApartmentTherapy.)
Aljaferia Palace, Spain
Simple travel keepsake idea--sand, dirt, or rocks in matching glass jars, sitting along a mantel/shelf.