What are some interesting topics to write a blog about?

For blogging ideas, see these posts for tips and inspiration:

"Developing Your Blogging Identity":
http://www.dailyblogtips.com/developing-your-blogging-identity/

"20 Types of Blog Posts - Battling Bloggers Block"
http://www.problogger.net/archives/2005/11/29/20-types-of-blog-posts-battling-bloggers-block/

"Lack of Ideas? You’ve Got to Be Kidding!":
http://www.dailyblogtips.com/lack-of-ideas-youve-got-to-be-kidding/

"A Simple Way To Develop Writing Ideas for Your Blog"
http://www.bloggingtips.com/2009/05/01/a-simple-way-to-develop-writing-ideas-for-your-blog/

"How to Choose the Perfect Blogging Topic"
http://www.sparkplugging.com/sparkplug-ceo/how-to-choose-the-perfect-blogging-topic/

"9 Steps to Better Blog Post Ideas":
http://www.dailyblogtips.com/9-steps-to-better-blog-post-ideas/

"Use These 10 Tips to Write Your Most Popular Post Ever":
http://www.dailyblogtips.com/use-these-10-tips-to-write-your-most-popular-post-ever/

"Six Steps to Stress-Free Blogging Habit":
http://www.dailyblogtips.com/six-steps-to-a-stress-free-blogging-habit/


FREE BLOGGING SERVICES:
Blogger/Blogspot (http://blogger.com ), Wordpress (http://wordpress.com ), Livejournal (http://livejournal.com ), Vox (http://vox.com ), Typepad (http://typepad.com ), Travelpod (http://www.travelpod.com/ ), Tumblr (http://www.tumblr.com/ ), Yahoo! Shine (http://shine.yahoo.com - already registered just go to the site)


FREE SOCIAL-NETWORKING SERVICES WITH BLOGGING CAPABILITIES:
MySpace (http://myspace.com ), Facebook (http://facebook.com ), Multiply (http://multiply.com ), Xanga (http://xanga.com ), Windows Live Spaces (http://spaces.live.com/ ), Yahoo! Profiles (http://profiles.yahoo.com - already registered just go to the site). Bebo (http://www.bebo.com/ ) and Gaia (http://www.gaiaonline.com/ ) are sites geared toward teenagers.

copy a cook book, and do all of the recipes in it in 365 days and blog about it.

You could blog on your life, if its interesting and has new wild things happening often,
Your experiences.
Blog about something your an expert on, what you enjoy most, one of your most loved hobbies.
For example, celeb gossip > if you seem to know whats happening and celeb gossip interests you, you could expertise in that!
Fashion > if you know the latest trends, catwalk dates, clothing companies etc.

Some free sites:
Blogger
Wordpress
Xanga
Tumblr
Live Jounral
Mind say
New blog
20 six
Open Diary

^ Just a few
I hope this helped. Check out my blog for some inspiration.
Have a good day =)