Tutorial for Developers: Text Input Methods
This page is started due to a request for such information.
Please remember that the OLPC is targetted to children in many countries using many different scripts and keyboard layouts. They will have no need of strange input methods but will type naturally in their native language. If you are developing on another platform such as Windows and you need to enter UNICODE characters you can use the Alt-key and numeric codes as documented in Wikipedia and here.
In addition, Windows and other operating systems have a character map application that allows you to view the full array of Unicode characters available in a given font, as well as copy and paste them. There are also several 3rd party utilities available to do this job.
However, the best way to deal with this is to either install support for the target language and keyboard layout in your OS, or to stick to your native language using gettext for all text strings so that they can be translated later. The Development issues page discusses how to do this.
However, if your goal is merely to test some Unicode data handling, there is a much easier way to enter text. Simply use Google to find sites in target scripts, for instance a Thai newspaper. Then cut and paste from the web browser. This works if you have a good Unicode font like Gentium installed and your browser is configured to use it as the default.