Inside Loops
Well folks, this is the one that started it all. Starting as a message on a board, it slowly expanded into a full guide. This covers normal "inside" loops. Preparation, equipment, how they work, and some troubleshooting tips.
Hop the Fence
Hop the Fence is a bit like the opposite of normal loops. However, I'd venture to say that they feel fairly different and take almost the same amount of time to learn, regardless of if you can already do loops.
Reach for the Moon (Shoot the Moon)
Reach for the Moon is fairly different from all the other tricks in this list. It travels in an arc above the head instead of a full circle. It also works well with butterfly yo-yos. It takes a lot of practice, but is great fun once you get good at it. Lots of advice in this guide.
Punching Bag
Hop the Fence done out in front of you, requiring much more force than hops or normal loops.
Vertical Punches
Punches done straight upward. These are often incorrectly called "Vertical Loops" on trick lists.
Two-handed Inside Loops
A lot of tips for doing loops with two yo-yos at once. Lots of advice and exercises for preparation and actually doing them.
Sweet and Sour
A somewhat technical essay about how yo-yos wind and unwind and how this affects throwing, catching, and different kinds of loops. There is no math, though, just some observations, so don't worry too much. =)