It is good to clean your bike chain once in a while to get the grit off. I use stuff made by MEC, called Bio-Cycle and a chain cleaning mechanism, also by MEC.. There are many different types of chain cleaners on the market, but this one seems to work for me.
How it works: Basically you fill the cleaning liquid up to the line in this handy little chain cleaning mechanism. You then attach it to the chain itself. What is nice about this is that you don't have to take the chain off!
There are brushes inside the mechanism that clean the chain on the outside and inside the grooves/between the chain links too. I also use a toothbrush to clean the cogset, derailers, and the chain rings. I do a few cycles with cleaner in mechanism, then I use water in it to clean the chain of the cleaner, I do that 3 or 4 times or until the water being used is not dirty after using it to rinse chain.
I then dry it naturally for a bit, and afterwards, apply some Tri-flo bike lube. It keeps my chain moving without wearing the chain out sooner then necessary or getting rust on it. No squeaks allowed on my bike! ;)
For all those new cyclists out there, do NOT use WD40 to oil the chain, it is not meant as a lubricant for chains and will actually wear it down faster as it attracts dirt. The lube I use has teflon in it to keep off the dirt.
This my posting for a second event- Do maintenance on bike for the LGRB Summer Games.