Deciding what camera gear to take traveling is always a trade-off.
I've flown thousands of miles on some trips with a 4x5" view camera, tripod and pounds of other equipment, on other trips with a point-and-shoot that fits in an Altoids tin, and with just about everything in between.
At one time my luggage exceeded 50 pounds, at another it was barely over 20. Traveling with the lighter load was definitely more enjoyable.
Flying to Cape Cod for a family holiday or Hawaii for your honeymoon, you may want to take less equipment and spend more time with your kids or spouse.
Driving to Yosemite for a photography workshop you might not mind lugging and keeping track of a bit more gear. But even so, you still may want to limit the amount of equipment you take. At some point having more gear with you can actually get in the way of your photography.
So where should you start in deciding what to take? Why at the end of the process of course.
What is end result that you hope to get out of the photography you will be doing on that particular trip?
Who will you be sharing the images with?
Will you only be showing them to friends and relatives or viewing them yourself to remember the great time you had?
Will you be sharing them with a wider online community, entering them in competitions or selling them?
Will you be printing them or only displaying them online? How big are the largest prints you will be making of them?
All of these questions will determine what level of quality you will strive for which will be one of the factors influencing what gear you will need to take. If you will only be sharing a few of them with your family on a computer screen or in 4" x 6" prints, you may be able to get away with taking a small camera and nothing else.
Another factor influencing your choice of gear to take is what you enjoy taking photographs of. If what you love most of all is photographing birds in wild settings and that is one of the goals of this particular trip, be prepared to take a large camera, large lens and tripod. If you will be mostly making scenic photos of travel destinations, a wide variety of camera can be suitable for that. If candid photos of people in dimly lit nightclubs or pictures of relatives in their homes (which are also often very dimly lit for photography) is what you most enjoy, taking a camera with a faster lens may be more important.
How far will you be traveling and how will you be going? If you are driving, there is really no limit to the weight of equipment you can take. If you are flying, biking or hiking, you should really work to make sure you are taking the minimum amount of gear needed to get the photographs you want.
Plan your equipment based on the majority of photos you want to make. If you are primarily making pictures of people and landscapes, do you really need to take your extra-long lens just in case you find an interesting colony of birds up in a tree. If you do end up missing one or two shots is it really that terrible? If you are a professional photographer and your job requires you to get those photos that is one thing, but if you are making photos for the fun of it, will it really be more fun for you getting that one bird shot or traveling lighter for the rest of your trip?
Even if you own a DSLR and a bunch of lenses, consider leaving them at home on long trips and taking a point-and-shoot camera.
A few years ago I was contemplating taking my DSLR with me on my honeymoon to Hawaii. I knew that if I did, I would want to buy a longer lens to photograph some of the birds and wildlife I would see there. But none of the longer lenses that I was looking at seemed to be available for under $600 and they would also have added quite a bit to the weight of an already heavy camera pack.
Although I ended up making many really beautiful photographs and having a lot of fun doing it, I knew that I was not going there with the goal of creating the world's most stunning images of the islands. I knew that many professional photographers had already spent much more time and effort creating great images there and what I really wanted was simply fun images that I could look at to remember our wonderful time there and perhaps share with some friends.
However, if I had it all to do over again, I really don't think that I needed the extra-long lens on that camera (a Canon Powershot SX20IS) and really wish that I had spent the money on a Canon G11 instead, a camera with a shorter lens but with many more useful features for general photography. Yes, I would have missed a few images that could only be made with that longer lens but I really don't think I would have missed them that much.
I also realized while making those bird and wildlife images that at this time in my life I really don't have the patience to be a great bird photographer. To get really good bird images, not only do you have to carry a fair amount of equipment, you have to be willing to sometimes stay still in one spot for ages, watching the birds and waiting for just that right moment.
I do use it on driving or hiking trips closer to home when I don't have anyone else waiting around for me to set it up and take it down. But not so much on longer trips.
I do often use a small portable tripod though on either of my point and shoot cameras, either the Ultrapod for my pocket camera or the Ultrapod II for the larger P&S. The smaller one especially fits easily in my pocket, sets up in seconds on any nearby surface or straps to a pole or tree for instant stability.
Even if you can't stand to go on vacation without your SLR, give a thought to only taking a small kit lens and a fast prime lens (a 50mm 1.8 for example). See if your neck doesn't feel better after a day of only carrying that around and you don't feel freer not having to worry about where you camera bag is every minute.