What software to use with Canon 500D?
There is nothing wrong with DPP. And it's free.
Many prefer an Adobe product. Photoshop Elements 11 is just starting to hit the shelves. It's excellent and a steal at $99. You can download a free trial (1 month-no strings attached) at Adobe. It has an excellent and complex organizer. Or it will simply download to "My pictures" in a variety of ways. It has a great editor as well.
Then there is full-blown Photoshop and , also, Photoshop lightroom. My opinion for a beginnere is PSE 11.