In the last 15 years, astronomers have found almost 400 planets orbiting stars other than our Sun. These extra-solar planets have a remarkable diversity of orbital and physical properties, many unlike planets in our own solar system. Even in this exotic menagerie, close-in extra-solar planets stand out as unusual and puzzling. These planets have masses ranging from several Earth masses to many Jupiter masses, but orbits that are at least 10 times closer to their host stars than the Earth is to the Sun. Because they are the easiest planets to detect, close-in planets provide much of our current information about physical and orbital properties of extra-solar planets, so understanding their mysterious origin and evolution is important for understanding planets in general. Within such proximity to their host stars, close-in planets are especially susceptible to the effects of tides. Tidal deformation of the planets by their host stars and of the host stars by their planets can affect the planets' orbital and thermal evolution. For example, tides can circularize orbits and cause them to decay. In many cases, tides may have already destroyed many close-in planets by causing them to crash into their host stars. As tides change the orbits of these planets, they can also heat their interiors. This heating may cause gaseous planets to become inflated, or may drive vigorous volcanism on rocky planets, as on Jupiter's moon Io. Tides can also help strip the atmospheres from gas giant planets that wander too close to their host stars. In fact, there are indications that the first unambiguously rocky extra-solar planet discovered, CoRoT-7 b, may actually be the remnant rocky core of a tidally stripped gaseous planet. In this talk, I will discuss our rapidly evolving knowledge of close-in extra-solar planets, and highlight the important and complex role played by tides.