I just finished a project along these lines, running cat6 from my office to the garage on the opposite side of the house, including running through about a 25 foot expanse between the house and the garage with PVC conduit.
The hardest part by far is simply digging the trench to lay the conduit, and that's not saying much as I did that in about an hour. Since the distance wasn't very great, I assembled and glued the conduit outside the trench and set it into place, gluing gentle curved bits to the ends to help the cable pulling process.
I started by drilling holes in the garage and house and putting in PVC conduit body units on the outside.
After sealing them down with a generous heap of silicone, I laid the previously glued conduit in the trench and cut the vertical sections to length (I left them overly long to avoid having to measure the depth) and glued them into the elbows mounted to the buildings.
After that I gave the glue about an hour to dry. I could have started reburying the conduit but I was paranoid something would go wrong and I would have to dig it up as it was my first time. Then, I took a tiny bit of foam tape and wrapped it around a pull string to form a small plug, which I shoved in the conduit. Then, I attached a shop vac to the other end and sucked the string through the buried section, then taped my cat6 to it and pulled it through.
The project probably took about 2 hours total apart from filling the trench back in which I conned my wife and 4-year old son into doing for me while I was at work.
I'll post pictures of the finished product when I get home.