Regarding the extensions listed at http://extensions.joomla.org is that every possible one available that is listed there or are there more available outside of that site?
It's not possible that that can definitely be the list of every possible one available. It's just not logical to think it is. Therefore, you have to assume that there are more available outside of that site...
I think only some extensions not available in joomla official site, ie. joomblog for some reasons they don't put it there anymore but you still can find it in other sites.
Actually thats a very good point, i hope i didn't sound too naive when asking im still reading about Joomla having recently become interested in it and so far im impressed with the availability of extras for it and the amount of users. I just did, my god its awesome spoiled for choice. Thanks, i imagine some developers and companies may prefer to keep theirs on their own sites only when distributing them.
There are some Joomla plugs that aren't listed in the extensions directory. Notably mamblog and it's associated plugins. They were removed because of some butthurt over code changes and uninstallation procedures. There are others useful components that have suffered this same fate. Check the joomla forums for additional drama.