I also enjoy procrastinating with youtube a lot Here are a couple that really help me to not get any work done
Fact Fiend - Start watching for the crazy facts, stay for the host. Most, if not all, of their facts are completely useless trivia, but OH are they fun facts! The host is someone who hates the entire "Business Side" of youtube with a passion and he doesn't keep that fact a secret. Their show is very amateuristic, which is what makes it so great. If you are in doubt I highly recommend watching their Colonel Sanders episode. ProJared Plays - A lot of people know ProJared from his game reviews, but he's also an incredible let's player. I especially like the videos where he plays trading card games. Both his Magic: Shandalar and pokemon TCG let's plays are good series to start with. If that's not your thing I would like to recommend his Final Fantasy 1 series.
Door Monster - These dudes make funny sketches. Most of their sketches are based on video games. What I think categorises them the most are their brilliant punch-lines.
Internet Comment Etiquette - Ah yes, Erik. His whole thing is making "Turorials on how to properly comment on video's". As you might expect he isn't very serious. This is an awesome channel with an awesome concept that is too difficult to explain.
I hope you'll find them enjoyable