Low light photography+moving objects?

I'm using a nikon D3000 to photograph a friends band. I don't want to use the flash because i feel like it takes away from the ambiance so my question is, how can i take a sharper picture of my guys without using the flash. I set the ISO speed to the highest setting but is there something else that can help a little. I know i won't get amazing shots where they are completely still without buying a better camera. I just want some suggestions.

Nothing wrong with the D3000. You need a faster lens which won't be cheap. In the meantime, try setting the camera to 'aperture' and opening the lens up (low f-number F3.5), up the ISO to 1600, lowest zoom (maybe 28mm on the standard Nikon D3000 kit lens) and remove any filters, even protection filters, from the lens.

A lens capable of F2 or even faster (lower number) is what you need but difficult to find for DX format and very expensive.

You are going around the world to get across the street. Meaning that with a DSLR, the LENS is the most critical element regarding your results. Having to use flash and extreme ISO are all by-products of not having a fast enough lens. You need a prime lens with an aperture of 1.2 to 1.8. And you will not have to worry about the flash or extreme ISO.

A WARNING: Remember that you are concerned with the light on the subject NOT the light on the camera because the stage where the band operates should be relatively well-lit. At a recent Moody Blues concert I used my Nikon P500 compact rated at 200ASA and shutter speed at 1/60 to gain acceptable quality 10 x 6 2/3 images.
Unfortunately my compact doesn't have RAW so I was unable to correct colour casts in PIPping (Post Image Processing) but the stage colours weren't all that unacceptable.

The best advice I can offer is the old faithful - "trial and error" but remember that the higher the ISO the greater the noise /grain that will be produced and you will have to balance the higher ISO against the level of acceptable noise. That is why a course of "trial and error" is the best advice I can offer.

ISO has nothing to do with blur. ISO has to do with the sensitivity of the sensor or "film" to the light. To stop motion you have to use your shutter speed. The kit lens probably isn't going to be adequate for this. You need a good fast lens that will handle low light.
SHUTTER SPEED is what stops motion. I'll give you some guidelines for shutter speed at the end. The shutter speed is how long the shutter is open. If it is open for a long time-the subjects can move or your hand can move and that movement is recorded as blur. The faster your shutter opens and closes the less motion can happen.
You also need to remember that in band photography proper exposure is relative. If the room is dark that is how it should be depicted in the photograph.
You will need to use a shutter speed of at least 1/125 if the band members aren't moving and probably at least 1/250. F/ will need to be f/2.8 and your ISO will probably be about 2000 to 2500 or somewhere around there. If it is a particularly dark stage you will max out your ISO. If the stage lights are on you may be working at ISO 1600.It just depends on the light.

Guidelines for shutter speed:
If you are hand holding the camera and are steady your shutter speed should never be less than 1/80.
If your subject is alive never slower than 1/125
If your subject is alive and moves no slower than 1/250
If your subject is alive and runs no slower than 1/500

Open the aperture wide open is the best I can suggest. You won't get a really sharp picture though, because your depth of field will be very shallow.
You can use the flash and include the ambiance, you just need to extend the shutter speed and burn in the light.