Uchronia.net: The Alternate History List - Originally known as the 'Usenet Alternate History List', version 1 of Uchronia was first posted on the Internet on April 11, 1991, to the Usenet newsgroup rec.arts.sf-lovers. Back then it was a plain text file about 30 kB long and a new version was posted to Usenet once every month or two. The idea for creating Uchronia was first conceived in late February 1991 and much of the first version was based on information provided by Evelyn Leeper. Evelyn is still submitting entries today. Uchronia moved onto the World Wide Web in 1995, but for the next two years was just a slightly modified copy of the same material that was still being posted to Usenet. In early 1997, Uchronia became Web-only. It received its current name late that year, at about the same time it was converted to the spiffy Web version you see today, which is extracted dynamically from a 1.1 MB text database.

UCLA Language Profiles - These are profiles of natural languages, with sections on origins, modern statistics, orthography, and more. The profiles include maps, and are very well written.

UCLA Phonetics Lab Archive - An excellent site for conlangers looking to incorporate unusual sounds into their languages. "This web site contains recordings of many of the languages that have been investigated by members of the UCLA Phonetics Lab or have been made available to the lab by other scholars. It forms a database that includes several hundred of the estimated 800 possible speech sounds in the languages of the world. The aim is to present contrasting sounds so as to provide illustrations of the range of the linguistic phonetic abilities of mankind."

UCLA Phonological Segment Inventory Database (UPSID) - A collection of web pages for each of the UPSID languages listing the phonological inventories of each language, showing the phonological segments by feature and referencing the other languages that have each feature. These pages are derived from the assertion files in the MacProlog implementation of UPSID. That implementation could be the source of some errors, as could my conversion from that implementation. Feedback welcome.

Unicode - Also see Unipad.

Universal Declaration of Human Rights Translation Database - The Universal Declaration of Human Rights translated into over 300 languages.

Universal Language Dictionary - The Universal Language Dictionary is a multi-language wordlist with related concepts arranged in categories.

Universal Translator Assistant Project - Motto: "Using the technology of today to bring the theories of yesterday to the languages of tomorrow." This Java program will "relexify" the text window using the language you choose: Vulcan, Klingon or Romulan. It will replace English words with the appropriate word if it knows one. If the word is Vulcan (or Klingon or Romulan) and it knows the appropriate English word, it will return that. Otherwise it will return the word surrounded with [brackets].

UPSID MacProlog Interface - A Prolog Interface to UPSID, for the Macintosh. Here's a description of the design of the UPSID data set.

Urban Dictionary - A dictionary of urban slang. However, it can be crude, and if you have problems with language, you might be offended by some entries. However, it is very enjoyable.