www.wordpress.com and www.blogger.com - both are simple and free for personal use. It's a "proper" blog system too, nothing like Twitter or Facebook .
Not sure which one to opt for, but as they're both free, why not try out both and then choose the winner?
If you really like it and use it often you could upgrade to the paid versions to remove advertising, but I'd certainly start off free and then go from there. You can use your own domain name and other benefits if you do that, from what I remember.