Blogger

Blom
"The Ajax instant messenger for your blog".

Jaiku

Terapad
Blogging and more.

Tumblr
"Tumblelogs are like blogs with less fuss. Tumblr is your friendly and free tool for creating tumblelogs". Very nice mini blogging application, excellent for link blogs.

Twitter
"What are you doing?" Very popular micro blogging.

Wordpress