From Krollchem in the comments at MoA:
S-400 (SA-21) systems:
There are two S-400 complexes guarding Khmeimim consisting of 16 missile launchers per complex (32 launch ready missiles range 350 km)
S-300 (SA-20) systems
Russia has seven S-300VM missile systems defending Tartus and aboard some warships (range 350 km)
Bastion (K-300P) anti-ship coastal systems (Yakhonts)Russia has deployed perhaps two batteries of 18 launchers at their naval bases (72 launch ready missiles – range 350 km) Russia also has K-300P systems on it Project 11356 frigates
Syria has two batteries consisting of 18 launchers which carry two 3M55E Yakhont supersonic cruise missiles. (72 launch ready missiles -range 350 km)
Kalibr (SS-N-27 Sizzler)
Russia has Kalibr long range missiles on all their frigates either 3M-54E1/3M-14E: (300 km range) or 3M-54/3M-54T: (660 km range)
Russia had previously provided 40 Pantsier-1 missile systems to Syria with 12 missiles loaded per system (480 launch ready missiles – range 20 km)
Subsequently, Russia has also deployed an unknown number of Pantsir S2 air defense systems to its Khmeimim airbase in Syria (range of about 40 km)
The Pantsier-2 may have been upgraded to add four directed sub-rockets to each missile for a total of 48 missiles per Pantsier launcher.
Russia has an unknown number of Buk-M2E systems and perhaps the new Buk-M3 in Syria.
Syria has received a total of 48 launchers of Buk-M2 surface-to-air missiles. (192 launch ready missiles – range 40 km). I believe that there is a BUK-M3 variant under development that carries more launch ready missiles per vehicle.
S-125 (SA-3) (Pechora-2M)
Syria has about 145 Pechora and 12 Pechora-2M each with four missiles per launcher. (628 launch ready missiles- range 32 km).
Same as was used by Yugoslav Army 250th Air Defense Missile Brigade to shoot down a F-117
S-200 systems (SA-5) (upgraded)
Syria has two S-200 batteries consisting of 44 launchers at Kweires airport (range 350 km). A Syrian S-200 missile was used to shoot down an Israeli F-16.
Syria has 195 2K12s systems with three missiles per launcher. (585 launch ready missiles – range 22 km))
Syria had 14 batteries consisting of 60 launchers with six short range missiles per launcher. (360 launch ready missiles – range 15 km))
Russia has installed both the land based systems (SA-9) and integrated them in their ships at sea (SA-N-9). The launchers come with either 8 or 16 missiles with a range of 16 km
Syria has a number of the older Tor-M1(V) systems with 4-8 launch ready missiles – range 12 km.
Russia has at least one Iskander nuclear capable ballistic missile systems in Syria -range 400-500 km. These are ship killers along with the Zircon missiles to take out carriers.
9K35 Strela-10 (SA-13)
Syria has 35 launchers – four missiles per launcher, reload time 3 minutes- range 5 km