The "Instituut voor Nederlandse Lexicologie" has in her TST centrale a resource where people with a need for lexicological content can choose what they need. All this material is copyrighted and it is made available at the lowest possible cost. The material is the result of many scientific projects and it is considered basic material for lexicology based on the Dutch language.
There are other resources that have importance to people interested in lexicology. Logos in its dictionary provides a rich tapestry of words with translations. In its link to wordtheque, you find the words in its context. In the philosophy of Logos, this often provides as clear an idea as a definition would do. A link to publicly available resource is not available through the resources of the TST centrale.
In the Kudoz open glossaries of Proz, you find a rich resource of hard to translate words. When you start looking for resources that have a relevance for the creation of dictionaries, there are many resources that are not created in a "scientific" manner. Practically they can be extremely usefull. It is a shame that the scientific resources are not Free and consequently that they make the "unscientific" resources unavailable for the enrichment.
Anyway, as long as these resources are used side by side there is nothing that stops the research of lexicology. As the Wikipedias are a rich resource of contemporary language, and as its content is categorised as to subject matter, it is good to know that scientists are free to use it for their research. I checked it with Jimmy Wales and he was happy to confirm this.
Tomorrow I will be going to Berlin. We will talking about interfacing the Ultimate Wiktionary using the TBX standard..