[Cecil]

If you already have access to a WordPress site, then that should work fine for a blog. When creating pages with it, you can set it to be password protected, and only give the password to the people you want.

As far as a wiki, MediaWiki is a nice way to go if you have your own hosted space. (I recommend hosting your WordPress site yourself anyway, it allows better control and a bunch of other plugins that aren't accessible to the WordPress hosted version.) MediaWiki is easy to set up, is well documented, and works exactly like Wikipedia.

If you are looking for good hosting companies, I would recommend HostMonster any day. You get unlimited bandwidth, unlimited storage, unlimited email accounts (if you need them), and unlimited databases (not to mention it's secure). If this isn't in your budget at the moment, however, remember that both MediaWiki and WordPress need SQL servers to run.