I got about 6 hours in, Post 2 is BS just to let you all know;
List i can confirm:
Businesses (Property/Not all have interiors)
24/7 (unmarked, loads)
LTD (unmarked, loads)
Liquor Store (unmarked, loads)
Tattoo Parlor (marked, 2 or 3 variants, several)
Barbershop (marked, several)
LS Customs (marked, several)
Clothing shop (marked, 4 variants (?), several)
Blaine County Bar (Marked/Drinking/Darts)
Strip Club (Marked/Dances/Drinking/ATM)
Bugstars warehouse (unmarked)
Heist Planning Warehouse (unmarked)
Subway system/station (unmarked)
Weed shop (unmarked)
Docks (various interior locations)
Simeons Car Dealership (unmarked)
Cable car station (marked)
There is more.. but we haven't done much missions yet, since i'm sharing game time with my mate (he got it early this friday), Various people say the stadium has an interior as well.. guess ill find out tomorrow.
Didn't count the cinema since that doesn't have a true interior.
Mission interiors (most anyways) stay enter-able after completion.