Wordlists

Word lists are an invaluable tool for creating your own languages. Here are some of the best.

Dublex Word Menu - This list contains the 400 most productive roots; these 400 were carefully researched over several years of langmaking and have been used to generate tens of thousands of words. This is the best place to start, because you will be able to use these roots again and again as you coin new words for your language.
Universal Language Dictionary - For the more ambitious, the ULD offers over a thousand roots with side-by-side comparisons to English, Dutch, German, Esperanto, Tsolyani and other languages. In fact, LangMaker.com has licensed the ULD and bundled it with LangMaker/Win for easy word-generation.
Fantasy LEX file - At long last, a lexicon suitable for creating your own fantasy languages! Compiled by Duncan Duchovy for use with LangMaker/Win for easy word-generation.
Latin & Latin LEX file - Useful for creating your own Romance languages, though you'll have to ignore long vowels (they're not marked - care to volunteer?). Also thanks to Duncan Duchovy.
Swadesh LEX file - The core words used to compare the time elapsed between a daughter language and its parent, used in glottochronology, the "carbon dating" of languages
Roxhai - A schematic vocabulary.
Basic English - The subset of English used in the controlled language called Basic English. Less useful in language building, due to the polysemy (many meanings) of each word listed.