I'd like to mention some of my favorite software the I use for teaching, arranging, transcribing and practicing.
1. Finale Notation (Coda Music). I use this all the time to write examples out for my students, and also to write charts for my groups.
2. Band-in-a-Box (PG Music). This is a GREAT way to learn tunes. You've really got the check out the new real tracks feature.
3. Amazing Slow Downer (Ronimusic). For transcribing and practicing. You can slow music down without changing the pitch.
4. SmartMusic (Smartmusic.com). GREAT for helping students get through those band books.
5. Apple's Garage Band (www.apple.com). Super easy way to record and share tracks with my students.
6. iReal B. I use this program on my iPhone to practice tunes on the run. It's great because I can practice tunes no matter where my location might be.