The Unearthed Arcana "sprint" is over, and the column is going to slow back down to about once a month, leaving us with quite a lot of material to try out... after adding the feats from the latest article to my tracking list of available 5e material, I did some counting and here are the numbers of various stuff. The totals include material from PHB, DMG, UA articles, SCAG, and adventure/campaign supplements.
Classes: 12 base, 3 variants, 1 prestige, 107 archetypes
Races: 29 base, 11 variants, 39 subraces
Backgrounds: 26 with 4 variants
Various features and options (only those that were expanded beyond core):
9 Fighting Styles
57 Warlock Invocations
5 Totem Warrior animals
13 Downtime activities
Spells: 316 core, 74 extra
Rules modules (non-core):
Encounter Building variant
Players Make All Rolls variant
Quick Characters variant
Traps Building variant
...probably forgotten a few
Note that these are approximate totals, because of various reasons: some material was slightly (or more than slightly) revised, some is likely superseded by other stuff, and "modern" options are bundled together as a single module.
We know that UA material isn't official, but much of it is actually usable.
I am interested in knowing what is your current choice of allowed material in your campaigns. I'll add a poll for a general check, but I am interested in the detailed list as well! Naturally, you might be running more than one campaign with different stuff available, in which case for the purpose of the poll just consider all your campaigns together.
Secondarily, I am interested in which options have been actually used in your game. If you write a checklist of what is allowed, you can mark with asterisks what stuff has been eventually already chosen by the PC or used by the DM.
Edit: I am not considering homebrew or 3rd-party material here, only WotC to keep it simple, but if you modified materials from WotC then feel free to count it in.
I picked "many options: 20-80% core", because I basically ignore UA but will allow anything from SCAG/EE/Volo's. Probably closer to 20% than 80%.
I'd allow most of the UA racial feats though--that's the first UA I'd seriously consider including in my game. I think it fills a needed gap for dragonborns, half-orcs, dwarves, etc.