An essay on thread with links
If you are a beginner quilter I am sure you have stood in front of your favorite quilt shop's quilting thread area not sure what you need. The amount of threads available can boggle the mind and they all serve a different purpose, depending on the project you are working on.
http://www.beginners-quilting.com/quilting-thread.html

Q-Links: Thread

Adjusting thread tension
This sitye is placed here for one purpose.  Although the blog is full of good quilting hints, there is a link right at the beginning, to another site dealing with thread tension that is supper in its content and illustrations.  So, enjoy both blogs.  Click on link below.
http://www.flynnquilt.com/workshop/FreeLessons/

A very interesting blog on thread.  Highly commercial, however, contains a lot of text , no illustrations, with links imbedded in the text.  Worth your wile if you have plenty of time.
A quilter's thread options are truly mind boggling. Thousands of color choices are just the beginning, and possibly the easiest aspect of choosing thread. Beyond that, you'll find threads specifically for quilting, and discover that hand quilting threads have characteristics that aren't a plus for machine quilting tasks. Click on link to read more.
http://quilting.about.com/od/stepbystepquilting/tp/thread-tips-quilting.htm

A bit commercial,  however provides good insight to picking thread for different designs.
There has been a lot of recent chatter about how to select the quilting thread color for scrap quilts or high contrast quilts or quilts with clear light, medium and dark fabric. This is my take on the topic, but first let me just say, I like to see the thread!
http://www.berninausablog.com/read/how-to-select-a-quilting-thread-color

Quiltwithdonna.com is the host for this program.  Click HERE to visit the host website.  You will love it.

A good discussion, without illustrations on different threads and when to use them.  Click on link.
If you are a beginner quilter I am sure you have stood in front of your favorite quilt shop's quilting thread area not sure what you need. The amount of threads available can boggle the mind and they all serve a different purpose, depending on the project you are working on.
http://www.beginners-quilting.com/quilting-thread.html

If you really, really want to learn about thread this blog is worth the time and effort.  It's complex and detailed, but worth the time if learning about thread is important to you.
http://www.allpeoplequilt.com/blogs/apqstaff/tag/quilting-notions/