Blogger is the platform I use most frequently. They have greatly improved the look and feel of the blogs, so I guess I am a creature of habit. . .but I am willing to try others. . .maybe.
My Tumblr: jheil65
Wordpress is probably the second most popular platform besides Blogger. They have clean looks and are just as easy as other platforms. The reason I don't use them is that the free version does not allow my to embed videos and other content in a post, I can only add a link.
Posterous is another platform that produces visually cool blogs. They now have Posterous Spaces. I have an account, but haven't used it much.
Edublogs is another blogging tool that is very educator friendly. I didn't find it as easy to navigate as the other tools, but I like some of the layouts I have seen. They also allowed for tabs way before Blogger ever did. . .I feature that I can no longer live without.