Adult Webmasters Netplace

This is the most famous and widespread blogging software in the world. It is easy, reliable and free. Almost anyone can use it to create and run its own blog. Lots of additional stuff like templates and plugins can be found all over the net. The only two drawbacks of Wordpress is some vulnerability to hackers attack (not because it has bad security, but because it is so widespread) and comparatively slow code (but I think that you won't notice it unless you have really big network.

If you either don't trust freeware, want solid support service or planning/running blog network you will definitely should check this software. Blog Organizer allows to setup blog in less then 1 minute and it is possible to operate hundreds of blogs using this scripts. All possible SEO optimization, rss, pinging and link exchange tools are already included in this program, making it ultimate tool for every pro blogger.

Here you can find hundreds of various plugins for wordpress, some of them are ultimately useful and others not. The only advice is to use only really necessary plugins in case if you have blog network, otherwise multiple plugins can overload server
Here is the list of useful plugins (however you can find many more that you would like)
All in One SEO Pack - very good search engine optimization plugin
Google XML Sitemaps - auto sitemap generator, very useful tool
My Link Order - easy to use links organizer
Robots Meta - creates robots.txt file, lots of additional options, my choice
SEO Friendly Images - if you post any images on your blog you will benefit from it
StatPress - statistics plugin
WordPress Database Backup - plugin that automatically backs up your blog and sends to your mail.
Ultimate Plugins Smart Update Pinger - advanced pinger for wordpress, which replace built in pinger
SEO Smart Links - quit useful plugin which automatically makes internal links, also have some additional SEO options
WordPress Related Posts - adds related posts to every post on your blog (via tags)

Several hundreds of various themes for wordpress absolutely free - just download and activate

Another great script for blogging which allows any blogger to almost fully automate most of his duties. It can automatically put rss/atom feed content on your new or exiting blog. It can automatically rewrite it and make unique. Besides it can interlink all your blogs in SEO way and does lots of other useful thinks.

The ultimate scripts for link and traffic exchanges. It can do everything possible to make link exchanges easier. It is possible to control link exchange process on hundreds of your websites from one place. All possible linking schemes are supported. Besides, this script counts in/out clicks, automatically checks reciprocal links, supports multiple niches exchanges and many more. One of the best deals for every serious webmaster.