A sheet or two (if staying in youth hostels).

A small flashlight.

Earplugs (for street noise in hotel rooms).

High-factor sunscreen.

A pocket alarm clock (for those early morning departures).

An inflatable neck-rest, to help you sleep on long journeys.

A multi-purpose penknife.

A needle and some thread.

Plastic bags (to sort your baggage, make it easier to pack and unpack, and keep out damp and dust).

Items for a basic first-aid kit are listed under "Health".