Very convenient means of transport provided your pet likes it !
As far the cats, hamsters, rabbits and other small pets are concerned, it is highly recommended to put them into a carrying box. You can also add some feliway 2 hours before departure that you can spray in the whole box so your pet can relax (there are natural hormones). Don’t forget to water every two hours your pets with a bottle of water and a bowl that you would bring with you in the car. If you take a break on the road, don’t ever leave your pet alone in your car with the windows closed ! take him with you or work in shift with someone else to get him out of the car.
You pet can travel with you provided you get a ticket for him. According to the websites and the countries, count a few euros per pet.
For the small pets, you can travel in cabin with them. Look at the website of your airline company.
Be careful if you decide to have your pet travel into the baggage compartment, we recommend you to control the conditions of this travel by looking for reviews on this company on line to see if there has been a precedent; in certain countries, the owners can find their pet dead at their arrival at the airport due to a lack of care of your pet by the airline staff. When this happens, you have very few actions to undertake. If the company is not reliable, we recommend you to take the boat, safer !