Like the previous posters above me have said, Wordpress and Blogger are the two big ones. I use blogger only because I heard about them first and like how easy and user friendly it is. It's 100% free including hosting. You can purchase your own domain name for around $10 a year from a site like GoDaddy if you want your own URL. I highly recommend your own domain name if you're serious about blogging.
I've played around with Wordpress and liked it a lot and would probably prefer Wordpress if I was starting out. There seems to be a lot more features and addons that you can do to customize your blog. The only downside that I saw is you have to pay for your own hosting which should only cost around $5-$20 per month depending on your traffic.
|