Everyone wants to write for TechCrunch, but you have to work your way up to those big sites. It takes a reputation and lots of past blog posts.

You'll want to tier the sites you've just researched into 3 categories: Beginner, Intermediate and Expert. Go after them in order as you develop your reputation and skill as a blogger.

This is one of my favorite quotes from Jason Fried's Rework. It applies very well to the guest blogging situation. Make sure you start off niche.