Confirmation that there are now three sides:
Syrian rebels and al-Qaeda-linked fighters battling each other at key checkpoint in Aleppo - Washington Times
But the extremist nutters have fallen out with each other! ISIS (The Islamic State of Iraq and al-Sham) and al Nusra are the two main nutter salafist groups. ISIS think al Nusra aren't extreme enough. And al Nusra think that ISIS are too extreme.
Al Nusra?s Syria Strategy; Update: FSA declares war on ISIS ? 2.0: The Blogmocracy
So we are on the very verge of a four way war.
There are other factions on the ground including Hezbollah, the Kurds, Christians and Druze. All armed and fighting. Alliances are constantly shifting, depending on many factors including who has the most money/arms. Soldiers often switch groups. Large numbers of fighters have arrived from Iraq, some fighting on the Sunni side and some on the Shia side. Afghani fighters are also arriving now they have beaten the UK/USA in their own country. Messy doesn't even begin to describe what is happening.
Israel is the biggest factor. They are a regional superpower and are already engaged in a undeclared war with Iran. Assad and Hezbollah are both Iranian clients so Israel wants them both beaten. The big car bomb in a Hezbollah district in the Lebanon this week looked like Mossad was involved. Creating trouble between them and the Sunnis. And there have been repeated Israeli air strikes against Gucci kit.
In the diplomatic world it appears that the USA and Russia are getting much closer (despite Snowden). They both have a huge vested interest in acting against islamic extremists.
Interesting times.