Aside from getting more light in the room, there's not really anything you can do. You can try using a third-party camera app, like Nightcap, to try and boost the capabilities of your phone, or Camera+, to modify your photos in post-production and possibly increase their fidelity (just as you could take your pictures into your PC/Mac and edit them in Photoshop). You will, however, be limited.
Until cell phone capabilities increase substantially, your options are few. My best advice is to try to get as close to your subject(s) as possible and attempt to capture as much light as possible. If you can rest the phone on something stable to minimize shake during long shutter speeds, do it. As rough as it can be, those are still the best ways to get good pictures in your situation.
Oh, and avoid zooming. You're usually better off taking a full picture and cropping in post.