Stationery can be extremely expensive overseas; the formatting of paper sizes also typically differs. Many other countries use the A4 standard instead of the US Letter standard. Bring any pen, paper, and other supplies that you might want to use.
Electrical adapters: many laptop and other portable electronic devices work on international electrical systems and require only physical adapters to connect to the plugs. Use of some devices may require a voltage converter. See World Electric Power Guide for an introduction to the concepts and the relevant table of systems. Power strips may not function on the international system because of voltage and frequency differences.
If you intend to use a bicycle abroad, consider shipping your own bicycle or bringing your own helmet and locks to prevent spending the money unnecessarily overseas.
Clothing availability and sizings may vary internationally. Plan to bring everything that you will need.
Making international phone calls can be tricky. See CountryCodes.com for more information on this. Other computer based Voice Over IP (VOIP) solutions are also useful: Skype and Gmail (Hangouts) permit internet based phone calls and are two of many options.