After reporting on how to obtain your offline installation of a great online dictionary, I want to point out how you can create an offline installation of a great online encyclopedia. I stumbled upon an article that describes just that. You have to download a Wikipedia dump. The rest is done by the package provided in the article. Be aware though that you will need around 9GB of storage during the preparation. Moreover, it took 24 hours to complete on my computer (1.7GHz Pentium-M Laptop). After that you you will just need the split dump files and the index. I put the index into a SquashFS container to save considerable space on in. I ended up with a compressed local Wikipedia installation (without images) that is relatively quick and inhabits around 4.1GB of HD real estate.