So many options. WordPress is about as simple (from a end-user perspective) as they come, it isn't necessarily lightweight, but it's more lightweight than some other options. More importantly, it has a very active following and vibrant development community, and it's based on the LAMP stack, so hosting is very easy to come by.

I second Wordpress. It's also easy to modify if you'd like to make changes that haven't already been made by others through the many plugins and templates available.

Big fan of ExpressionEngine. Was on the fence, but used it for a critical project where simplicity was the critical point, and it was a dream to work with. No issues, and nothing that limited our extensive development ideas from coming to life.

Depends on the site, and how much free time to have to support him.

You might be able to get away with something like Jekyll, or else give your friend a template and a quick lesson in editing HTML (h1, h2, p, img, and a tags, plus testing and uploading should be about it...).

Option 2 is some sort of hosted CMS, with his domain name on the front - wordpress.com, posterous or tumblr, something like that.

Those suggesting these big systems like Wordpress... lol. Wordpress is far from light. It does a lot, but it is also a monster of an application.

I wanted something ultra-light, so I made rant:

http://github.com/lrvick/rant

Maybe look at http://www.cmsmadesimple.org/ or http://radiantcms.org/

Something like http://pulsecms.com should be perfect. Install takes less than two mins

Thanks a lot for your options, I will let you know what I went for.