One program that I often have used to break up band practice recordings into individual mp3 files is Nero WaveEditor. It's a free program found here.
http://www.nero.com/enu/downloads/Scroll down towards the bottom of the page and it's listed under the free programs.
The reason I use that program is because sadly, Sonar still can not use markers to export individual songs as a batch. That's what Nero WaveEditor does very efficiently. It will also convert wave to MP3.
So for me the procedure goes something like...
1. Do a quick mix in Sonar and export 44.1/16 wave of entire practice.
2. Open the wave file in Nero WaveEditor and place track markers (the markers missing in Sonar).
3. Export to individual tracks as MP3 which is a batch process in Nero WaveEditor).
I realize your trying to do this fast as your friends are sitting around waiting. You also mentioned not wanting to use markers. But this is the quickest way I've found to of this. I really like the wave editor in Nero. I found its interface very quick using the mouse wheel to quickly zoom in and out to place markets accurately.