http://www.growkind.com/glass-pipes-bongs.html
Once you try this method of cleaning glass you will wonder how you ever lived without it. This is by far the easist method to clean glass pipes we have ever found.
1. Take your glass pipe and place it in a ziplock baggie.
2. Add a fair amount of table salt to the bag. Probably at least 3-4 tablespoons. You cant really use too much.
3. Add rubbing alcohol to completly cover the glass pipe.
4. Seal the ziplock bag and shake it for around 5 minutes. More or less time will be required depending on the amount of cleaning your glass pipe requires.
5. Rinse the glass pipe under warm water to clean off the alcohol and any remaining resins.
That's it! Your glass is now clean. If your pipe is very dirty it may require a couple treatments but you will be surprised how easy it is to clean glass pipes, glass bongs, glass vaporizer handpieces, you name it using this method!
Just Google searched it and this is the first thing I found. Probably some more if you do a search but this looks pretty easy and you don't hafta go out and buy anything to clean it with.