The Wikimedia Foundation manages the servers for several projects. Wikipedia gets almost all of the attention, and the others get almost none, even though at least some deserve a lot of it.
My personal favorite is Wikisource, a collection of freely-licensed texts that were already published elsewhere. It is similar to Project Gutenberg, but with somewhat different focus and style.
But there’s another project, which deserves more and more attention and praise as the years go by: Wiktionary. Even though i love printed and digital dictionaries, i never became a frequent editor of Wiktionary for two reasons. The first reason is software: MediaWiki runs Wikipedia and all the other Wikimedia projects. It is quite well suited for Wikipedia, which thrives with long encyclopedic articles sorted in a very liberal tree of categories. It’s much less suited for a dictionary, which requires a rather different model of storing, linking and sorting the entries. Some attempts were made to improve this, for example, the many templates and gadgets developed locally in the English Wiktionary and the OmegaWiki project. Both of them have nice ideas that go in the right direction, but still have many implementation problems.
The second reason is problematic methodology. It’s a hard problem to explain, but i’ll try: Writing a good dictionary is a lot harder than writing a good encyclopedia. When you are writing an encyclopedia, you can base your article on one or more reliable source about the nature and the history of a certain subject. The limits of what needs to be described in an encyclopedic article, at least for important subjects and fairly well-known people, are generally easy to determine. Dictionary compilation works entirely differently: to make a good dictionary, the editor must possess a large and representative collection of texts in a given language, to find all instances of a given word, to sort them into groups and to describe the usage of the given word. Such resources are very hard to find, and there are very few people who have the needed qualification to use them well.
Despite these problems, i find myself using Wiktionary quite often. Here are a few things for which i actually use Wiktionary repeatedly and successfully:
- English Internet acronyms: AFAICT, TTYL, IRL, FTW, AYBABTU. They often appear in emails and chat sessions, they are legitimate dictionary terms, and the Wiktionary definitions for them are usually accurate.
- Catalan, Spanish and Italian verb conjugation tables: I learn these languages, and i find the verb conjugation tables in Wiktionary complete and very easy to use. I have no reason to think that they have mistakes.
- Studying Dutch. I studied Dutch for a couple of months a year ago. Unfortunately i couldn’t find the time to go on with it – i hope to come back to it! – but while i did it, i intentionally tried to use the Dutch Wiktionary to find words in the translation tasks that i got as homework. I found all the needed words easily and the explanations and the translations were clear and helpful. Of course, words in homework for beginners are probably simple, but then beginners are probably the most important and frequent users of dictionaries. In any case, the Dutch Wiktionary did the job very well.
Another advantage that Wiktionary has over other paper and digital dictionaries is that it is very richly illustrated. Paper dictionaries usually have few illustrations, if at all, because they want to save paper. Commercial digital dictionaries also have few illustrations because their publishers don’t want to pay a lot of money to photographers and designers. Wiktionary doesn’t have either of these problems: Wikipedia is very richly illustrated thanks to the enormous amount of images contributed by people and Wiktionary has direct and easy access to the Wikimedia Commons – the same repository of Free images, sounds and video that is used by Wikipedia. And of course, Wiktionary is not made of paper.
So there: Wiktionary may still not be as strong as Wikipedia in completeness and in popularity, but it definitely deserves attention. And the people who work on it despite the enormous difficulties deserve a lot of praise.
Aharoni in Unicode 
Oh, the mythical Forcellini dictionary. :-)
You’re right about Wiktionary: it’s the first Wikimedia project I edited, in 2005, but I never really believed in it, until a few years ago, when I saw that somehow en.wikt managed to become a sufficiently structured and useful dictionary, which I thought impossible.
I never wrote my proposal for dictionary under https://strategy.wikimedia.org/wiki/Proposal:Make_Wikimedia_projects_scale but I believe that what’s needed is an initial critical mass and structure imported from an external source, on which to build. All the successful Wiktionaries did it at some point (most notably en, fr, ru) and with WMIT we’re currently trying to do the same for it.wikt with an old public domain dictionary.
http://it.wiktionary.org/wiki/Wikizionario:Importazione_dizionari_PD