I tend to be a bit the opposite of Dapleb, and pack what he'd consider a fair bit of crapola, but the TDM takes luggage pretty well. Several of my essentials have already been mentioned:
- Empty top box: it's important to make sure you have enough space for a baguette, some cheese and a bottle of wine, but I also find as a tour goes on the stuff I'd neatly packed in my panniers seems get bulkier as I rummage in it.
- Petrol stove: No worrying about spare gas canisters, and I keep a length of windscreen washer hose under the seat to siphon fuel from the tank, which has also been used when someone ran out of a fuel on a tour.
- Eye drops: I find a combination of sun and breeze really dries my eyes out.
- Stove top espresso pot: A fortnight of instant coffee is not my idea of a holiday.
- Self inflating roll mat: more comfortable than a foam one, lighter and warmer than an airbed.
- Aldi dry bags: fraction of the price of an Ortlieb and just as good, my tent and roll mat go on the back seat in dry bags.
-Packsafe: wire mesh bag intended to secure rucksacks, ideal to shove your bike gear in to lock it to the bike while you wander round tourist attractions in shorts and sandals rather than roasting in your bike gear. If you're paranoid you could also use it to lock the dry bags to the bike.
- Sleeping bag liner: Packs really small but adds a lot of warmth.
- Couscous and chorizo: take up no space, keep for ages, and are a tasty meal if you don't get round to buying more food.
- Satnav: Loads of people don't like them for touring but that's because they're not using them right, get one that can use waypoints and then sit in the campsite in the evening with beer/wine and maps planning a route for the next day and programming it in to the satnav, that way you can plot a route on fantastic roads and not need to keep stopping to check the map.
- Ignore the satnav: If you see something that looks more interesting than the road you planned, you're not a slave to the planned route. Some of the best roads I've ever ridden were speculative "that could be interesting" roads.
- Power to the tank bag: I have a DIN socket on the bike and then a cable that gives me a couple of USB sockets in my tank bag, means I can charge my phone/camera etc on the move but still get at them quickly.
- Scott oiler: Fill it up and home, maybe check the chain tension a couple of thousand miles later.
- GPS enabled camera: Somewhere between Andematt and Davos is the most beautiful picture perfect postcard village you have ever seen nestling in a lush green valley below snow capped mountains. I have no idea where it is though. I've since bought a camera with GPS so I see where I took photos.
- Archies Campsite POI's: This one was a game changer for me. A massive list of camp sites all round Europe that you stick on your satnav and it marks them as points of interest. It's only ever let me down twice, on the first occasion we just went to the next closest, and the second time what it had as a campsite turned out to be a Gite, but at a decent price with a friendly landlord a coupe of Dutch bikers staying there too. the main thing about using this though is that you don't need to plan where you're going to be each evening, just ride and when you feel like stopping find the nearest campsite http://www.archiescampings.eu/
- Camera backup: I've seen too many people lose photos due to a corrupted card, luckily I've only had it happen once and that was on the first day of a trip. Lots of options these days from dedicated backup devices, to cables for your phone, or go the whole hog and carry a netbook you can charge on the bike, and also use for route planning in AutoRoute/ITNconverter/Tyre/Basecamp and then upload to your satnav.
Sorted and on the Road Mick 
