Wow - just when I was waiting for some solutions to the numerous planning and documentation problems that are inherent in Sharepoint two come along at once, if you want to go the Visio 2007 route and have a look at this:
http://www.visio-for-sharepoint.com/VFS-Pages/VFS-Purchase.asp
You might like to hear someone saying that Visio is the way to go http://sharepoint.microsoft.com/blogs/mikeg/Lists/Posts/Post.aspx?ID=1524
And here is free wireframe to do site designs on
http://cid-1b6acb7b24d13da6.skydrive.live.com/self.aspx/.Public/Site%20Wireframe%20Template.vsd
There look to be a tonne more here
http://www.visguy.com/2006/12/05/sharepoint-planning-visio-diagrams/
but I can't vouch for this lot as I am sat at a mac so no go the Visio.
But wait those nice people at endusersharepoint use Mind Manager (which despite its frankly Orwellian name seems to be a very useful tool) - don't believe me ? have a look at this http://ow.ly/1aS1
