i suggest cardio trainer
I use cardio trainer, its is a free app. w/a gucci paid version. i have however, only used the free application as it seems to be plenty for me (im not that serious about my riding, im trying to be as good as i can be/get in great shape, but i cant justify spending $10 on an app that basically only gives you interval training advice, when their are free interval training applications on the android market, its not like i am a professional racer).
i have yet to find an android application that is solely for cycling, and i think one is long overdue. but cardio trainer works well for me because i also run, and cross country ski, and you can even manually input workouts (which i do when i go to the gym). when you use your droids gps w/cardio trainer on a ride: the application maps where you went on google maps, uploads all of your info to google health, and it even graphs your speed over time, in addition to giving you many pieces of information such as calories burned, distance, avg, high, and low speeds, and the app will go so far as too sort out the information monthly for you. another fun feature of cardio trainer are leaderboards, which is always fun to see how you stack up against random germans and japanese people.
I have also used runtastic, another free application which is pretty similar to cardio trainer, just more basic.
hope you enjoy your HTC (im assuming

phone!