What are some ways to wire rear speakers in a home theater system?
If you're installing in room where you can't drop above or below the room to run your cables, consider putting up crown molding -- it typically leaves a small channel behind it which is ideal for hiding speaker cables.

You can then punch holes in the top of the wall where you need to run vertically, fish the wires through, staple it up into the corner, then install the crown molding to hide everything.

You can also go the low route, and hide them behind your baseboards, but there isn't always a void behind them, so this could get a little messier if you have to trim away drywall (or plaster in older homes) to create a channel you can use.  You also have problems with baseboards if you have to go past any doorways.