OmegaT is a translation memory application intended for professional translators. It does not translate for you (software that does this is called "machine translation"). It features fuzzy matching, match propagation, simultaneous processing of multiple-file projects, simultaneous use of multiple translation memories, and external glossaries. Document file formats include plain text, HTML, and OpenOffice.org/StarOffice. It has Unicode (UTF-8) support (can be used with non-Latin alphabets). It is compatible with other translation memory applications (TMX Level 1).
Openbakery Translation is an internationalization tool for Java. Unlike standard i18n in Java, openbakery translation uses the text in the default locale as the key. There is also a tool which checks all of the source code for translations. This tool then provides a list of key/value pairs which have to be added to a certain resource file, and another list of pairs which can be removed. The translation works by simply calling a static method called "translate". The code works out of the box, without writing any properties files. You only write properties files when you really translate the program to a second language.
PHPLangadmin is a Web interface for editing PO files created by the xgettext program of the GNU gettext utilities. The messageids will be stored in a MySQL database. The user can add a translation for different languages for any messageid. PHPLangadmin can create the appropriate PO file for a selected language which the user has already translated. It features package administration to handle different applications, user administration, and language administration. It can parse output of the xgettext utility and create a language file for the translated messages.
Poedit is a gettext translation (.po file) editor for Unix, Windows, and OS X. It aims to provide translators with a simple, easy to use user interface with all the essential tools such as spellchecker or translation memory. It can also be used to manage translations for small projects.