Recently we started using StumbleUpon to promote our travel blog and it’s been so successful that I’m kicking myself that we didn’t do it earlier. In the past four weeks we’ve had three times as much traffic as we did in the four weeks prior. StumbleUpon now brings in most of our blog’s traffic and it’s become quite addictive for that very reason. What is StumbleUpon? StumbleUpon allows users to search web content via categories such as travel, marketing, camping,…