Hot Jupiters found to be losing mass due to extreme heat and stellar winds. These often have a cometary tail, or even a ring that forms around the star. This ring may even shroud the entire star system.
HD 209458 System - Has first discovered transiting planet which was nicknamed Osiris due to the (first detected) comet-like tail detected and the first exoplanet around a normal star to have its mass directly measured. Also the first Inflated Hot Jupiter found. The planet may be losing its outer atmosphere, or magnetism may prevent the ions from escaping. They detected water in its atmosphere (they had failed earlier), the first time this has been done for any exoplanet. 2nd Exoplanet with detected organic compounds; like HD 189733b, it has water and carbon dioxide, but it has a lot more Methane. Was one of 2 planets to have light directly taken and thus their temperatures read (over 1000K). Tracking carbon molecules with dopplar spectrometry caused it to be the first exoplanet detected to have winds, which are raging at 5,000 to 10,000 km/h. This is believed to cause hotspots to appear at terminators rather than at the star-ward facing point. Had one of the strongest water detection of the 5 exoplanets contrasted by Hubble in 2013, though still less intense than expected, probably due to dust clouds or a haze blocking its detection.
OGLE-TR-10 System - Contains a bloated Hot Jupiter expected to be losing its atmosphere. Noted for its similarity to the first transiting exoplanet. Thought to not be so bloated, but then confirmed to really be bloated. Found to have the lowest measured surface gravity of any of the transiting exoplanets, considerably less than Earth. 5th confirmed OGLE planet. The first star observed to experience a stellar flare during the transit of one of its planets. The star is suggested to be active and have a high x-ray luminosity.
TrES-1 System - Contains the first transiting exoplanet discovered with the TrES amateur equipment and second transiting exoplanet close enough to have its atmosphere studied. It is the first Hot Jupiter that had the expected radius. Was the one of the first two exoplanets to have its light separated from its host star. Has a cloud or torus of particles around it. Tidal heating is predicted due to its eccentric orbit, but this has not seem to have inflated its radius.