Been playing around with a DSLR for the last few years. I end up taking quite a few photo's indoors, and have been roped in by relatives to photographing a wedding (scary!) and a couple of big birthday parties.
I bought a Sigma external flash with adjustable head, you can swivel it up/down and side-to-side. I reckon it's the best investment for getting decent indoor photos in low light. But only if you bounce it off the roof or similar, it's often too bright when used directly.
I recently had a nephews birthday party, and was able to compare:
- my photos with external flash bounced off the roof
- my photos with built-in pop-up flash
- my photos with fast lens (e.g. f 1.4 - f2.0) and no flash
- other peoples photos from DSLR's with pop-up flash
- other peoples photos with pocket cameras
I was really pleased with how my photos came out with the external flash.
If you're doing a lot of photos inside, or in low light, I can highly recommend an external flash unit.