I have shot many concerts for several bands. I used to shoot on a Canon XL-1 which I loved, but have just recently switched to a DVX-100a.

You will definetly want to get a 3CCD camera and don't waste your time with trick settings like "low light" or "night vision" like on most of the canon consumer cameras.

That being said, the Canon XL-1 was a great camera, but you said you don't want a "big, bulky" camera so that might not be your style. You could look at the GL2 (I don't know if it is 3chip) because it is smaller.

Also, a bit expensive, but the Pansonic DVX100A is a great camera (and smaller), especailly at low light levels. It shoots at 24p and cinelook, which gives it a cool film style. I'd look for either of these cameras used on ebay. You can get the XL-1's on ebay for 1000 and they are always in good condition because they were used by pros.

Some tips:
You've probably figured it out by now, but your biggest problem will be focusing. Because of the changing lighting on stage auto focus won't know what to do, you'll be fine for a minute and then the focus will go on you. Get a camera that you are comfortable with the focusing and turn off the auto focus. Many of the consumer cams focusing is awkward.

The XL-1 and DVX100 have a great focus becasue you can set it on manual and then push button to grab auto focus and let go of it to go back manual instantly, no clumsy switches, but there is also a focus ring like a traditional 35mm camera.

Also, set a white balance at the beginning of the show (if possible) in a lighting condition that is similar to what the show will be in. Use a large white card on the stage by the mics. If you can't, just use a white balance preset.

I recorded a documentary about a local band and followed them for 26 shows across 5 states. A year later they broke up and we shot their final concert on 6 Canon XL-1's. It was a blast! You can check out the DVD trailer at this website if you are interested in seeing some of the footage:
www.colorsmusic.com

have fun!