Anywho, lets talk business.
Question the first: Where can I find documentation on existing 2010 build activities?
Answer: You can't. Seriously, lame as this answer is, from what I understand there is no documentation to be found. Sorry.
Question the second: Is there an activity to deploy a website to IIS?
Answer: The answer is technically no, but you can do this via MS Deploy and then add some build arguments to kick it off. Check out this post which describes the process in pretty solid detail.
Question the last: What is the link to Ewald Hofman's blog post about creating custom activities that you failed to walk through because you forgot you had no internet connection?
Answer: You can find the specific post here, which is one of a series of great posts on customizing team build.
And that's it! This has been kind of fun, and makes me want to revive the blog a little, but I'm not making any promises. If you really feel like you need a little baboon in your life, check me out on twitter (@codebaboon).