Some sites that contain reputable blogging tips:

18 lessons I’ve learnt about blogging by Darren Rowse at Problogger

Ten Tips for Writing a Blog Post by Darren Rowse at ProBlogger

Converting one off Visitors to your Blog into Regular Readers by Darren Rowse at ProBlogger

Search Engine Optimization for Blogs by Darren Rowse at ProBlogger

31 days to Building a Better Blog Headquarters by Darren Rowse at Problogger

The Seven Deadly Sins of Blogging at the GreatNexus Webmaster Blog

The 7 types of highly effective bloggers

10 Journalism Tips for Bloggers, Podcasters, and Other E-Writers by Spencer Critchley

Handbook for Bloggers and Cyber-dissidents by Reporters Without Borders

Newbies at Bloggercon III by Rebecca Mackinnon (Audio File)