Dr. Higgins will teach you and help you teach yourself any language. It works like a quiz, asking you the translations of words and keeping score of your correctness. It includes a number of quizzes for self-study in different languages (English, Spanish, Finnish, and a bit of Japanese). It's very easy to add your own lists, thanks to a simple file format.
Voca is a vocabulary trainer for foreign languages. It allows you to create and manage your own word lists and share them online. You can make word lists for any language or for other things you want to memorize. It lets you do different types of exercises, including grammar, pronunciation, and picture tests. It lets you take tests with open answers, self-check, or multiple choice. Voca has support for multiple translations of a single word.
Vocabularium creates Spanish-English podcasts to help with vocabulary learning. A vocabulary topic and the subtopics which you want to include in the podcast can be selected. The program outputs a WAV file (or MP3 if Lame is installed) that reads a list of Spanish words and phrases with English translations based on that topic. Several vocabulary topics are built into the program. Under Windows, Vocabularium is designed to work with any SAPI 5 voice. Under Linux and Mac OS, it currently works with Cepstral voices, including the free demonstration versions.