Many GNOME and GTK+ programs offer translators the possibility to have their names listed in the about dialog. This is usually done by letting translators translate a particular string that then gets used in a "Translators" tab in the dialog. Please use the string "translator-credits" for this. Avoid using an underscore, since some translator tools always treat underscore as the encoding of an access key, and hence warns if the msgstr doesn't have an underscore as well, which in this case would be wrong.
Also, please remember that translators love being credited by name in release announcements. It gives them a nice, warm, fuzzy feeling, not totally irrelevant to further madness with translation efforts. There are also scripts (like this one or the other one) available for automatically extracting names from ChangeLogs etc.