North Face raincoat. Granted, I've only used it a couple of times so far, but both of those times have been when I needed to go to the station on my bike in a downpour, and it performed marvelously. Plus the water runs right off it with a good shake, so you can roll it up and stuff it in a bag (and it does squish down to practically nothing). I still think charging almost $100 for the things is criminal, but I'm happy with it.
Zip-up robe. This has been awesome for getting to and from the showers. I used it at camp for eight years and it's still going strong! Granted, if I had brought two or three big towels and no robe, I could just wrap my towel around me - I mean, the shower is about thirty feet from the door of our room - but this is thinner and saves space. Plus it's a great color (mint green) and has pockets for toiletries.
Speedo chamois. I've loved this thing since the first day I got it - it's sooo much easier than carrying around a heavy wet towel all the time - and it's coming in extra-handy here, since twice a week I have to employ multiple trains in order to go swim. For those who don't know what it is - it's one of those teeny towels you always see the Olympic divers use on TV, the ones that can absorb tons of water, then be wrung out and used again, indefinitely. Now that I think about it, I have two of them, and I probably could have brought the second one and used it for the shower, too, and skipped the 'normal' towels.
Also: portable laundry basket, travel alarm clock, Fossil purse, multiple DVDs, Stain Stick, small notepads, and my external backup hard drive. (I was extremely glad I had this yesterday, when I thought my computer was dead AGAIN. But then, for some reason, unplugging every single cord made it work. Go figure.)
Stuff I really didn't need:
My iPod speakers. I use them all the time at home, but here I only have one American plug, the one on the shoebox-sized converter, and that, 99% of the time, is used for my computer. (The other 1% of the time, it's for the Sony camera charger.) If I want to play music, I just play it through iTunes; that way I don't have to unplug my computer. As much as I complain about this laptop (its newest trick is freezing during recovery from hibernation), it does have truly decent speakers.
2 extra bathing suits. My Endurance one is made of special material so that it just keeps going and going without becoming see-through or stretched out. (My former roommate, the Olympic swimmer, claims she used one for a full year and a half, 10 practices a week, before it died.) I guess it's always good to have insurance, and they don't take up much room, but still - they weren't necessary.
Bikini. I don't know why I thought I would need this, but I did. I guess if I end up at one of those indoor water-park places, I'd use it - Dutch girls never wear one-pieces unless they're swimming competitively - but that hasn't happened yet, nor is it especially likely to.
Miniature converter (for things other than computers). Not only is it a piece of crap, but it is simply unusable. European plugs, by and large, are not flat against the wall the way American ones are, but are set in a circular frame and sunken into the wall by half an inch or so. More difficult to get your fingers in the way or accidentally do something stupid, I guess. The converter, however, is a simple gray cube with two round pegs jutting out of it. Ahem. Nothing to account for the circularity or the sunkenness. Therefore, the contacts don't reach the plug, and therefore, it's getting pitched out.
Beach towel. I did have the good sense to bring only one, and a thin one at that, but still. At the pool, I use the aforementioned Speedo chamois, and I brought two smaller-sized towels for the showers. I really didn't need another one.
Also: body lotion samples, iPod arm strap, Dutch grammar book, and all those 'but-they're-my-favorites-and-I-might-need-them' T-shirts.