There are thousands of different analysis and opinion pieces on what's going on. They broadly seem to fit into two camps: (a) it's because the rioters are Muslims and this is the beginning of a new effort aimed at an Islamic conquest of Europe and (b) it's because the French are racists.
I find it interesting that so many people on the 'right' are keen to paint this as some form of French intifada, as if the rioter's religion was all the explanation needed for what is going on. I'm not convinced, although many of the people making this argument are those with whom I'd generally agree. The reason I find this interesting is that many of these people are supporters of the war in Iraq, which is supposed to bring freedom and democracy to Iraq. Yet, if French Muslims cannot live peaceably in a Democracy, which is the implication of that argument, what hope is there for Iraq or any other Middle Eastern country?
I thought this Stephen Schwartz column was good (found through Instapundit). This discussion over at Slugger O'Toole's had some interesting comments on the religious make-up of the rioters.
I'd be surprised if the number of those rioting was 99% moslem. There are no official statistics, but I'd guess 40-60% moslem at most. Another point to keep in mind is that a lot of immigrants from former colonies like Algeria are in fact Kabyl [I added link because I didn't know what Kabyle was - IE], and not even necessarily moslem.