This might seem strange, but the lowest bounce rate in my blog comes from Stumble Upon visitors. And this is not surprising, since I think that Stumble Upon is the most accurate way of getting your blog to your exact target audience.
For example in the picture above, from my Analytics reports for last month, Stumble Upon visitors' bounce rate is 47.45% less than the blog's average. Demonstrating the accurateness of its interest/channel system.
In case you don't know what the bounce rate is, it is something quite meaningful for a blog's success, it is the percentage of visitors that only read/watch one page/article, so every blogger's aim should be to have a very low bounce rate, which would mean that users come, read one article, like it, and stay to read more.
Go check your stats for Stumble Upon visitors, and you'll see that what I say is completely true!