I don't know the specs on the HTC you are using however; not all chargers are the same. You can get USB chargers that are 2 watt (cheep ones from Wal-Mart and 7-11), 5 watt like what is supplied with many OEM products like the iPhone and my Motorola phone, and 9 watt chargers like I have for my Kindle. Chargers up to 12 or 15 watts are also available with more than one port so you can charge more than one thing at a time. The chargers that bbinder recommended are good chargers - look at them.
If you find your charger is getting warm or hot when your charging your device may be pulling more current (watts) than the charger is designed to handle. As the unit gets hotter, its ability to deliver power to the device is decreased causing a higher demand for power, causing more heat, further decreasing the chargers capability and the circle keeps going until the charger finally gives up! The better chargers will turn off when they get hot to protect the charging unit from cooking to death.
I would get a 7 to 9 watt charger (one port) or a 9 to 15 watt (2 or more ports) and a new USB cord (just in case your cord has an intermittent short that may also kill your charger) Check out Amazon, eBay or your favorite electronics/phone store. Don't let the sales man tell you "this will work" without seeing the watt rating on the package. The charger will only deliver the power the device demands, you will not hurt your device by using a 7 watt charger even if the one supplied was only a 5 watt. The charging circuit inside your device has a micro processor in it that regulates the amount of energy being delivered to the battery.
I hope this helps and good luck to you!