Cloaks - Tutorials

Cloaks are a costuming staple for gamers and Ren. Faire goers. They're oddly simple yet confusing if you're a novice sewer. Many folks have written some tutorials on how to make them without having to purchase a pattern. Some are definitely clearer than others.
Here are a few of the best I've found.

The DIY Guide to LRP site has a number of great tutorials on costuming in general. More specifically, they have not one but three classic options when it comes to cloak construction.
The Basic Rectangular Pattern - This is simple to make but looks less sophisticated. If you have never sewn a stitch in your life this is your choice, as it avoids more complicated shapes and cutting.
The Semi-Circular Cloak - This is very common and drapes the body better than the basic rectangular cloak. It's still fairly simple, and the site guides you through things fairly well. It requires a bit more fabric, but in my opinion the end result is worth it. A simple and interesting addition to this pattern is to add another semi-circular cut, following the same instructions, of about 1/4 the length. Add it as top layer for a pseudo-capelet.
The Opera Style Cloak - Most cloaks you would buy at a costume store are probably this cut. They're constructed to account for shoulders, and thus drape the body very well. Only slightly more complicated than the Semi-Circular cloak.

Ultimately your choice should depend on your concept for the outfit, and which style would best suit the overall ensemble.

Fabric Choices
Wools, satins, and velvets are three fairly obvious options. Panne is an inexpensive velvet look alike, though it can be a bit tricky to work with because of its stretchiness. A personal favorite of mine is Moleskin. It's fairly easy to work with, and can look either rugged or elegant depending on what you do with it. It can be harder to find, but comes in a variety of color options.
Lining a cloak will definitely give it a more polished look and feel. Choosing a flashy contrast can really make it pop, if that's what you're going for. Another option is to add a border or fringe.