Afrikaans
Afrikaans, spoken in South Africa, is a descendant of the Dutch originally spoken by colonists from the Netherlands. It is the youngest language in the world that is used as a nation's official language. Wikipedia offers a lengthy linguistics-oriented introduction to Afrikaans. One university professor in the U.S. offers a site with fairly complete advice and materials for those interested in learning the language. Afrikaans.be is a blog and LitNet is a site devoted to Afrikaans-language books and literature.Frisian
Frisian, spoken on the islands northwest of the Netherlands, is English's closest living relative. A classic example of a Frisian word would be "tsiis," which is spelled oddly (to English eyes) but means "cheese" (there are many other examples and comparisons here).Wikipedia has an introduction to Frisian and a separate page on Old Frisian. Here you can download a complete Frisian course for beginners, which also offers a YahooGroup for those following the course.
Once you've learned a bit, you might enjoy a Frisian-language literature portal. Here are some Frisian-language games, like hangman and anagrams.