One thing that is definitely worth organising if you travel frequently is a travel wallet. For some this may seem obvious but hopefully for some others it may be useful. Below is a pic of my travel wallet.
Passport - two things I always try and make sure I have with regards to my passport is that it has a sticker on the spine. I use this to make it out in a pile; it's just a marker so I can spot it quickly. This is useful when you find your passport being mixed in with a number of others at things like checkpoints or if you're travelling in a group. It's a quick marker that allows you to keep tabs on it. I also try and always have my passport contained in a clear plastic bag. This is designed to keep it dry and clean from spillages etc or if your bag/wallet goes in the water. Another thing to check with your passport is to keep an eye on the expiry date (you normally need six months remaining) and the number of pages you have left (it's good to have at least two clear).
Spare passport photos - always worth having a few available as you never know when you're going to need them on forms, visas, applications etc. I learnt is the hard way having to find a passport photo studio in Beirut and the whole process being an utter faff. (Besides they're good to have a laugh at later - both of those in the above picture were from a while back now)
European health insurance card/air miles cards – just good to always have these handy.
Spare business cards – never know when you might need them and it’s good to always know you’ve got back-ups
Spare dollars – Dollars are king. Wherever you are in the world they can help get you out of a sticky situation.
Spare home currency - always good to have emergency cash in your home currency in case you return to find your wallet or bag lost.
Yellow Fever Certificate - a few countries need this for entry. The number of times I've seen people getting hassle because they don't have it on them – for that reason alone it seems always carrying it with you when you travel.
Vaccinations card - it's always good to know what you've had and what your up to date with
Paper clip - if like me you carry a spare iPhone for local sims then this is always useful. Getting the sim out is much easier if you have a paper lip to hand!
Copy of your passport and copy of your travel insurance documents (although worth keeping a copy elsewhere too otherwise it kind of defeats the purpose!)
That's all for now - hopefully there's some little nuggets there that will be of use to someone! If you found it useful you might want to read this article on what's in my travel 'grab bag'.