I may be missing something here (be great if I am), but it seems to me that the content of the Ubuntu Wiki - which contains some great stuff - is not licensed under one of the common 'shareable' licenses, like CC, GFDL or OPL. Neither the front page nor any of the several random pages of content I checked has a license declaration that I could find, and the "Legal information" link in the footer takes you to the general ubuntu.com legal info page. So as far as I can tell, the license on that page - which is basically "for anything other than personal non-commercial use, apply to Canonical" - applies. That's a bit unfortunate, and against the open source spirit of collaboration, if it's true. I had a couple of people check my sanity on this one, and asked in #ubuntu-doc, and no-one could find anything to the contrary.
I got onto this by looking at the Ubuntu debugging procedures page, which is great. We're looking at improving the Fedora wiki pages on what information to include when reporting bugs on particular components, and it would make sense to just re-use the Ubuntu community's work here rather than spend time re-do it all ourselves which could more usefully be spent elsewhere. But if I'm right, we can't.
If anyone knows that I'm wrong here (or can explain why there isn't a less restrictive license, if I'm right), please do comment. Thanks!