A continuously updated list of small, optional "extras" you might find useful while traveling. Most are obvious, but as new products get released, I'll try to update this post with the "latest and greatest" options for each category.
Nano Day Bag
I pack a SeaToSummit Nano Day Pack - while not a necessity with an already small backpack, I do find myself using it frequently, as you'll often be separating stuff into "things I'm bringing" and "things I'm not bringing" - it makes life just a little bit easier.
Water-Proof Electronics Bag
I keep my electronics in a 13L Sea-To-Summit Dry-Sack; it gives me peace of mind, helps keep things organized and comes in handy for any planned or unplanned water-based activities. Note the optional sizes; I use the 13L bag because it fits my laptop, but there are lots of options.
As a cheaper/smaller alternative, consider a floating water-proof phone bag - again there are lots of options, just make sure it's IPX8 certified (waterproof up to 100ft/30m).
Check out my post on Choosing a Backpack for more detail and recs.
I don't use compression bags, although they're great for organization, I prefer to use my wash-bags to compress and pack my clothes (see The Minimalist Method), but if you're packing a larger backpack and like how they look, to each their own! Search packing cubes on Amazon and pick your favorite color.
Wireless Bluetooth Sleep Masks
Sleep masks are a godsend when you're sharing a room with strangers, and I highly recommend keeping one in your pack; the one I'm currently using is this LC-dolida, or search "wireless Bluetooth sleep masks" on Amazon.
I'm sure you already have headphones, they're cheap and available everywhere, but I didn't want to assumptively leave them off the list.. search "in-ear wireless headphones" on Amazon.
I don't normally use reusable earplugs, I find them less comfortable than the throw-away plugs you can find at any convenient store, but I do keep a pair in my bag just in case; search "reusable sleeping earplugs" on Amazon.
Considered an absolute must-have by many travelers, a multi-functional buff comes in handy as a face mask, neck warmer, headband or sleep mask.
Foldable Phone Stand
There are a bunch of options for foldable phone stands, and they are extremely useful; for an inexpensive option, check out the iMangoo kickstand; or for a more durable, flexible and long-lasting option, the Pocket Tripod Pro; or search "minimalist folding phone stand" on Amazon.
Toiletry Bag /w Hooks
You can easily use plastic bags for your toiletries, it's cheap, easy to replace and the epitome of minimalism; but after months and months of travel, I can't imagine having a toiletry bag without hooks, and for as little as $7 dollars, I think it's worth it.
This low-profile, magnetic Speedy Mag Wireless Charger looks useful and promising, but I can't seem to find the specs or charge capacity, so check it out at your own risk!
Nomad Base Station Pro.. if you have lots of toys that need charging.
RFID Protected Wallet & Key Holders
If you do a lot of cooking in your hostel or Airbnb, you may find a collapsible spork to be a must-have; there are full-size and folding titanium options, or if you're worried about getting flagged for the metal on flights, there are plastic options as well.
Not all hostels have kitchens, but those that do will almost always have kitchenware that you can use, but if you're really worried about it; you may want to consider collapsible cups or bowls as well.
More to come soon!