Update for the status prior to the Singapore race weekend (I'll try to keep doing these as we're at the stage of the season where it can really have an impact). As we already knew, Kvyat became the first driver to take a penalty for using more than 5 elements by having to use a sixth ICE at Monza. Perhaps wanting to maximise results at their home grand prix, all but one of the Ferrari powered drivers used at least 3 new elements during the Monza weekend. This leaves the Ferrari guys very light on ICE, TC, MGU-H and CE units for the rest of the season... On the other hand, the Mercedes powered teams introduced almost no new components having used a lot of fresh units at Spa. It's also very telling that not a single Mercedes powered driver had used all 5 of their units of any type going in to the Singapore weekend.
Remember the information is relevant to before the start of the Singapore weekend, so this is the status at the end of Monza. Cells highlighted green indicate where new units were used during the Monza weekend.
The acronyms mean:
ICE - Internal combustion engine
TC - Turbo charger
MGU-K - Motor Generator Unit Kinetic (KERS)
MGU-H - Motor Generator Unit Heat (Energy recovery from turbo)
ES - Energy Store (Batteries)
CE - Control Electronics