A cardboard box works fine, in fact the basic rule is a properly packed bike is pretty safe...no matter the container... the reverse holds true for improperly packed ones as well. Here's the basic drill for safe packing, regardless of shipping container. (items with * not needed with most travel cases):

• Indelible marker
• Bubble wrap, big or small bubbles are OK.
• Packing tape*, get a big roll, and a small one to pack in your carry-on bag in case the airline asks you to open the box at the airport.
• Cardboard bike box*, take a six-pack of microbrew down to your hard-working shop mechanic and have him save you a box or two, the american bike company boxes are the best, get two and put one inside the other if the cardboard is flimsy or they've got a few holes or tears.
• Toe straps, remember those? 2 or 3 are fine. Large rubber bands, masking tape.
• Tools to disassemble your bike, pedal wrench, 4-5-6 hex keys, etc.
• Closed cell foam pipe insulation, get enough different diameters to cover all the frame tubes.

Start by removing the pedals, (remember the left one is reverse threaded) set them aside to be packed separately (maybe in your carry on luggage along with your shoes?).

Remove the seat post/saddle assembly, (mark the seatpost with a piece of tape so you can reinstall it in exactly the same place) wrap in bubble wrap (use the rubber bands to secure it), set aside. Next loosen the stem fixing bolt (you may need to tap it with a punch or mallet to get the wedge or plug to break free). If your bike has a threadless headset, loosen the pinch bolts and remove the stem after removing the top cap (a piece of PVC pipe cut to mimic the stem can be slipped over the steerer tube and secured with the top cap to keep the fork and bearings from falling free, or use a bunch of rubber bands to secure the whole works). Remove the front brake from the fork by removing the nut located on the back of the fork crown, reinstall the nut and wrap the complete caliper in bubble wrap. This way you'll not need to readjust the brake.

Now shift the rear derailleur into the big cog and the front to the large chainring. You can now remove the front wheel, take out the skewer, wrap it in bubble wrap and set it aside. Take an appropriate diameter piece of pipe insulation to match the fork blades and slide one end up the fork, then slide the other fork blade into the other end, making a U shape (you'll need to trim the pipe insulation to the proper length to allow the fork dropouts to sit squarely on the bottom of the U). Further protect this area with an additional piece of pipe insulation as this will protect the fork tips from damage while protecting the bottom of your box.

Now cover the remaining frame tubes with the pipe insulation, you can cover the crank arms and other parts as well by trimming the foam with a knife and securing it with the masking tape. If you label each piece of foam either by writing its location directly on the foam or the masking tape, you'll save a bunch of time repacking at the end of the trip.

Now, reinforce the bottom of your box with plenty of packing tape as you'll be dragging it around a few airports before you're done with it. Reinforce the handholds with extra cardboard by cutting a similar sized hole in a scrap piece and taping it in place from the inside.

Stand the bike on the floor just as it would sit in the box, leaning the front wheel against the left (non chainring) side of the frame. Position the wheel so that it makes as narrow a package as possible. Strap it to the frame with the toe straps, you can strap the crankarm in whatever position works best as well. Remove the stem/handle bars (this is where you're lucky that your bike shop left some slack in those ergo power control cables, if not, before you loosen the cable anchor bolts, try removing the cable stops from the down tube---just remove the little screws and pry the stops off the frame, then reinstall the screws to prevent loss, this will usually allow enough cable slack to get the bars out).

Get a buddy to hold the box open and upright while you lower the bike in with one hand while the other hand holds the detached handlebar/stem. Make sure the fork drops down to the bottom of the box. Now find a convenient spot to stow the handlebar, you might need to loosen the stem/bar pinch bolt to get it in without damaging anything. Put additional pipe insulation or bubble wrap anywhere contact between parts is likely, then note where the front axle contacts the interior of the box, here you want to add a cardboard reinforcement to keep the axle end from poking out during handling. Make sure the other end will not damage the frame or bottle cages.

Put the other wrapped parts in the box wherever they fit best and check the box for proper closure. You want some space between the top of the box and the bike if possible, add more pipe foam or bubble wrap to any potential contact areas, then seal it up!

Make sure you write your name and airline/airport destination on the box and that you bring the small roll of packing tape in your carry on luggage in case you need to open the box for airline inspection.

Using these tips will help protect your bike from damage even while using a travel case, we recommend installing a travel axle or old hub in the rear dropouts whenever the rear wheel is removed and strapping down the handlebar assembly with toe straps so it won't jump around in the box and damage anything.

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More travel chapters:

Guidebooks | Literature: what to read | The Bike | Packing your bike | Your Body: getting ready for the trip | Life in Italy | Bike Friendly Hotels