This is one of those things that are a manner of personal opinion but the two main ones that people like are Wordpress and Blogger. Personally, I like Wordpress because there are a lot of plugins and themes that you can use.
Where's a good place to find the best looking Wordpress templates and how do I install a Wordpress template
google is the best place to find templates if u have fantastico on your hosting that will do it automated if not just follow the read me its pretty simple
u need to download the themes and upload it to ur wordpress site root/wp-content/themes/ folder then activate the theme via Design>>Theme The same applies to plugin...upload it to ur wordpress site root/wp-content/plugins/ folder and activate it via Plugins tab in wp dashbaord If u change theme and plugins occasionally then use this plugin http://anirudhsanjeev.org/projects/oneclick/ which skips the method of uploading
Personally, I like WordPress the best because it is easy to use, has lots of addons available, also lots of support available if needed and it provides easy navigation for site visitors.