While waiting for a reply I'll try to type out some of the bigger rules:

The ball can only be moved forward by a kick or running it. If you the ball moves forward off of your body it is called a "knock". This typically results in a Scrum. The image below is how a team typically looks during a scrum. The other team would match this, but if they are on "defense" (meaning they are not putting the ball into the scrum) their line is flat. The off sides line at this time is the ball. This means that the opposing scrum half cannot pass the ball until your scrum half touches it.

So your scrum half puts the ball in. The hooker hooks the ball between the locks and the eight man separates the two scrum halfs. The scrum half takes the ball out and passes to the fly half and then a whole lot can happen. This is the typical way. The eight man could, for example, pick up the ball and run as well.

Rucks are a little harder to explain. If you have the ball and get tackled you have until the ref says "immediately" to release the ball. This is why when they are tackled the tend to turn back towards their team so they can place it closer to their players. Then people engage over the ball and this is called the ruck. Any number of people can be involved in this. You may only enter the ruck from the end and you may not touch the ball once engaged in the ruck. The back foot of the ruck on either side is the offside line in this case. One player will go to the back of the scrum and either pass it out or pick it up and run. This happens ever time a tackle is made. Also, unlike American Football, the tackler must bring you to the ground in order to be considered tackled. This means that if you get checked you can get back up and run. Lastly, if you are tackled and are quick, you can get tackled release the ball get back up and keep running with it, or the defensive player can do the same.

Trys can also be a bit confusing. In rugby you must put the ball to the ground under control for it to count. You get 5 points for doing so. You then get an attempt at 2 extra points. To determine where you kick from you draw a line back from where you placed the ball down and kick from there with a minimum distance from the try line (I forget the number). So if you place the ball between the uprights you get to kick from between the uprights. If you place the ball at the touch line, you have to kick from the touch line.

When kicking the ball the onside rule is also a little confusing. Whoever kicks the ball is the onside line. If you are behind him you are also onside. Once you are onside you remain onside. The furthest player up that is onside becomes the onside line. Once past this you may come into contact with the other team.