Every time I meet up with Jon he has something I want or think I need. I hate him for it, but love him for making my gadget collection insane. If you have unlimited money, which I don't, but I love my Epson P-2000, which I use as a viewer and an external download drive. It is so beautiful that I can sort through the images quickly or put the few that are amazing on a SD card and show everyone. So, that's my first recommendation if you have money to spare and want a neat toy to play with.
The best things to buy before a trip are tools to organize your stuff. For instance, Jon gave me some old Sucrets boxes I use to put batteries in. Wow, that helped so much. And then he showed me his filter wallet, I have a few filters, they were still in their original boxes, which got ridiculous in my bag for space, and that helped a lot. Now all are in that wallet and I can just keep track of all of them at once. So, things like that, to make your equipment easier to locate and store are key for traveling.