Fresh off my week-long stint in Europe, I definitely am glad I invested in some of the following items which came highly recommended to me by some of my backpacking friends and some great budget travel blogs.

Two Travel Adapters
One for your USB chargers and one that’s grounded for your higher voltage electronics.
For the USB chargers, I got the EZOPower EU Dual USB Adapter (available here, but currently out of stock, so this is similar). I liked having the dual ports because in addition to my phone, I would charge my external battery.
For the grounded charger, I got the QVS PA-C3 Adapter (here). The surge protection will keep your higher voltage electronics (read: your Chi hair straightener) from shorting. Keep in mind that some of your electronics may not convert well to foreign voltages. Check the manufacturer’s website before travelling, just in case.

Microfiber Travel Towel
If you, like me, are travelling on a tight budget, you’ll probably end up staying in hostels most of the time. And while there are some fabulous hostels out there, most are very much in the “get what you pay for” category. That means 100 or less thread count sheets, sharing a room with up to 11 other travellers and questionably clean towels. Microfiber is much smaller than traditional terrycloth and way more absorbent. It won’t take up much room in your suitcase and added bonus: it dries super fast! So you can hang it off your bunk when you leave in the morning and it will be dry in time for siesta.
I bought this towel in the 31×60 and 39×72 and had no trouble fitting them in my backpack. They were great and I didn’t incur the towel rental fee at one of the hostels I stayed in.

Flexible Luggage Lock
Now, I know every other travel blog you read will warn you about the pickpockets that abound in tourist attractions all over the world. I found that this little piece of hardware deterred a lot of theft and provided me with one less thing to worry about while I was trying to navigate a strange city and battling jet lag at the same time. I really recommend getting a cable lock because they’re so much easier to thread through the little openings on luggage zippers. I got this lock from Master Lock, but any small cable lock will do.