Bike Trailers
If you are like me, then you would probably want to be fully equipped on a loaded long distance bike tour. Bike trailers are great because of how easily they move behind the bike, as well as how much stuff you can fit in and on top of them. The number one manufacturer of bike trailers as far as I know is called B.O.B. and of every cross country tourist that I met while biking, each and every one of them was pulling a B.O.B. trailer. This is a cargo trailer, not to be confused with a trailer built to haul children.
When comparing trailers and paniers, one of the main benefits of the trailers is that it doesn't affect the balance of the bicycle and also avoids the pulls and drags of the wind much better than the panier counterparts. Paniers affect the balance of a bike fairly significantly; if the bike starts to fall sideways, it can be very difficult to correct and remain balanced. When the wind comes blowing in from the side (Cross-wind) the paniers get pushed around side to side and can make for a troublesome ride, and of course if there is a headwind, the paniers will act as something like a wall to the wind making it even more difficult to press on. That said, paniers are still very useful, however, you should refer to my page on paniers if you want more information on them.
Personally I recommend that every cycle tourist use a trailer.
BOB YAK Trailer
The only touring trailer that I can recommend is the B.O.B. YAK trailer. B.O.B. used to make a bicycle trailer called the COZ, which was basically one of those Rugged Rubbermaid containers fastened to a chassis (I own this one personally). The COZ wasn't tough enough to handle my 7500 Kilometer trip across Canada and eventually needed an ugly repair to make it usable.
However, the YAK trailers are considerably better designed and I saw dozens of them while I was biking across the country. The YAK trailers have an open metal frame design; equipment and gear is stored inside a yellow water-proof canvas bag. There is plenty of places available to attach bunjee cords if there is not enough room inside the bag.
The trailer is low to the ground and very easy to pull. Most of the time I didn't even notice that I was pulling the trailer.
I recommend the BOB YAK trailer for anybody planning a long distance bicycle tour.