That is awesome TG and a further testament to what happens when you provide solid, quality content over a long period of time. Your blog is very useful so I see why you're getting some Google love.
A similar thing happened to my flat stomach site last January. I was averaging about 780 visitors per day (in total, not just from google) then all of a sudden Google fell in love with me and my visitors increased by about 400 uniques per day the next month. It's pretty exciting when that happens.
This is very encouraging to people who are struggling with traffic and a great example of what hard work and good content can produce! Way to go!

I'm sure other members will see this as inspiration for their own sites and blogs.