I use MyxerTones :: Ringtones from your music! ---it's free, only requires an e-mail and valid phone number, and works like a charm. Upload your own music, you pick the portion of the song you want to use, and it sends it as a text message with a link to download on your phone. Fantastic.
I just use iTunes to crop out a part I want, save it then send to my BlackBerry through Desktop Manager. Been using iTunes for all my ringtones for every phone I had owned.
I use a freeware program called Goldwave. You can find it by searching for gwave512.exe or maybe by going to their site if they have one. It's free and it can do a ton of audio stuff to include cropping. Also, you can visit store sites like Walmart. THye give 30 second previews that you can download. (As long as it's the part of the song you want)
Does anyone know where to get just a simple "ringing" ring tone that's loud enough to hear. I don't like that "old phone" ring everyone has. I liked the old Nokia rings, or the one I used to have on my Treo.