The rebels have a good supply of ATGMs and an intermittent supply of MANPADs. They also have lots of explosives that they use in tunnels, home made weapons and IEDs. Some of this they have captured from the regime, but most has been supplied externally.
The Saudis and Turks have been involved to some extent, but by far the biggest benefactor has been Qatar, who have spent about $3 billion arming the rebels.
Initially a lot of the arms were sourced in Libya (by the CIA, who are organising everything) but the killing of the US ambassador in Benghazi halted this.
The next big source was Sudan and rumours are of Ukrainian aircraft freighting supplies.
But what has been very confusing is the vast preference that has been given to Jabhat al-Nusra over the Fee Syrian Army as recipients for all this kit. Early in the war the FSA were the dominant rebel force, but the supply of Qatar funded arms to al Nusra has seen them come from nowhere to become the biggest fighting force.
Al Nusra is an an Al Qaeda associate and is designated as a terrorist organisation by the UN, the UK, the USA etc. Yet the CIA has been organising their receipt of most of the Qatar funded arms.
Al Nusra are committing lots of atrocities, mass murdering regime prisoners and ethnically cleansing Christians and Kurds. A couple of weeks ago they took over some coastal villages and mass murdered the Alawites there. In all their captured territory they enforce strict sharia law.
So why are the CIA doing this? One theory is that the FSA are militarily ineffective. Consisting of local volunteers who want to protect their homes and deserters from the army they were unwilling to take up the bigger fight against the regime.
Al Nusra, in comparison, are extremely effective. Salafist extremists committed to Jihad with no concern for their own lives they are happy to throw themselves at the regime. For them the goal of establishing a caliphate is worth everything. Al Nusra have been reinforced with volunteers from many countries, hardened Chechen and Pakistani terrorists and lots of very experienced Sunnis from Iraq. As well as the British, Dutch, American etc islamic nutters.
Another thing that is surprising is the very low level of Iranian involvement. In Iran there are very many Shias who want to go to Syria to fight and their government isn't letting them go. The Iranian Revolutionary Guard is well over 100,000 strong and must be desperate to be allowed to get involved. There are a small number of Iranians in Syria, mostly guarding holy Shiite shrines. The restraint shown by the Iranian government has been impressive and surprising.
The USA and UK governments are planning their involvement right now. It could happen tonight or any time from now on. They are convinced (presumably by SIGINT) that Assad was responsible for the chemical attack. Some say he did this deliberately to terrorise his opponents, knowing that Russia and China would back him all the way, especially at the UN. But the USA/UK are bypassing the UN, using the Kosovo precedent. Just now they are putting assets in place and gathering target information. They have SF in place to help with the latter.
The USA have at least 360 Tomahawks in theatre and can easily deploy armed drones. As in Libya they will not put boots on the ground. The big question is whether they will bother using manned aircraft. LCRA is an unsinkable aircraft carrier and there are plenty of Turkish and Israeli (even Jordanian) bases that could be used. But to go down this route would take a huge commitment and if they just want to give Assad a bloody nose it isn't necessary.