So the album art that iTunes generates is pretty easy to work with if you want to make simple paper CD sleeves.
Here’s an overview of the printout and the finished sleeves.
The first step is to cut off the top and bottom, using the crop marks as your guide (don’t rely on the fold lines: if your printer doesn’t grab the paper just so, your cover will be a little off-center). Cut off everything outside the crop marks. 
Next, use the crop marks to trim the sides: you can cut off everything outside them when you do the sides. Then cut a small (1/4 inch) slot from top and bottom along the center, where the cover or sleeve will fold. Fold the sleeve in half along the lines marked. Then fold the resulting parts down along the top and bottom. Apply a glue stick (or Elmer’s if you prefer: you really don’t need much) and press the seam flat. 
Now you’re going to have to work with me here: I would take another picture to illustrate this but my digital camera didn’t make it home from a Christmas party last night. Anyway, glue down the thin tabs on the back side (where the track information appears) and press it down, then glue the other tabs and fold the sleeve together, wrapping the tabs from the front around the whole sleeve so they close around the back. 
Press out the seams (the handle of a utility knife works well for this) and you should be done. You should have a CD sleeve that looks like the one in the picture. The trick is using the crop marks to ensure it’s the right size to hold the media. The crop marks work just fine for that, though I sure didn’t realize that the first time I tried this.