So the first one is : BoxedThoughts. This site, is a little special to me, I've began writing my first "blog" here, back in Q2 2005. It's a quite long time, and it gives some good and bad memories when I reread all of them...
The main concept of the page is easy. You can post your thoughts in small brackects, but you're limited aroung 200 characters. It's not that much, but it's enough to write down you current thoughts. You have a one and half hour limit, for posting blogs. Teh most important features : You don't have a username, or anything that resembles to you, just a number. You can't post anything, what can be used to identify you (name, street adress, email and so on). And that's all... There's a raw stream, that can be read on the site, or using an RSS reader.
Why is it good? It captures your feelings, your thoughts, and you can reread them any time. It's not for the community, you're making it only for your sake, and that's what I love about this site. You don't care about your rating, the comments and so on, just about you.
I don't know how popular is this site, or how many users do it has, and I just don't care.
Recently they started an another version of it, where you have user names, and you can post your data, your name and so on... But I like the original concept much more.