garvinhicking wrote:No, serendipity does not have a feature of sub-blogs within a single blog.

Why?
With this feature Serendipity will be wonderful alternative to WordPress MU

garvinhicking wrote:Hi!

You can install the plugin "User Self-Registration" which is available via spartacus or http://spartacus.s9y.org/.

HTH,
Garvin

This plugin only gives opportunity register and write in main blog
Is there any plugin which gives to guests opportunity register and have own blogs?