This is what I use. It gives a bunch of links to sites that do stream it (presumably without ads, but I have AdBlock installed for Firefox, so I don't see any ads to start with). Some are more high quality than others.
This is another site a lot of people use. The layout sucks, but the streams are usually pretty nice quality. Once again, there may be ads, but I don't see them. (and I think this site has a "no ads" section for streams that don't have any ads)
If any of these sites say you need to DL some plugin, do not download it. You don't need to. Other than that, they're relatively safe to use. I've used them for 2 years now without any real issues.