Some others to watch out for:

1. Don't ask for "zip codes" only about 200 million people know what the hell they are. The rest of the world calls them "postal codes" (assuming they speak/read English.)
2. Don't assume that all postal codes will be in the same format as zip codes. Since most American developers also usually deploy to Canada which uses A0A 0A0 style postal codes this usually isnt a problem, but if you cant handle SW1 as a post code you've just eliminated some of the richest British people there are from using your service.
3. Don't assume that all telephone numbers are of the form (123)456-7890. That pattern is only valid in a few countries outside of North America and the Carribean. Some countries may have more digits, or even far less. In Germany for instance a phone number could be as few as 8 digits or as large as 12.
4. Don't assume that the street number comes before the street name. In Germany for instance its normal to say the street number after the street name. (I work in Wall St. 12 not I work in 12 Wall St.).
5. Don't assume that people will have a middle name for disambiguation purposes. In some cultures middle names are uncommon.
6. Don't assume that 12 hour time will be instantly readable by everybody. Support 24 hour time as well. Ideally let the user choose.
7. Don't assume that dates are in MM/DD/YY format. That particular date format is pretty well restricted to the civilian US market. Use "YYYY-MM-DD" and youll annoy a few traditionalist but never be misunderstood.