So you're looking at that neat M.2 gumstick SSD, but your motherboard lacks the necessary slot. Worry not: look no further than SilverStone's ECM20 PCIe expansion card.
This small expansion card has two slots for M.2 SSDs. The M-key M.2 slot will connect a drive directly to a PCIe x4 slot, while the B-key slot will let you plug in a SATA M.2 SSD, which connects to the motherboard with a SATA cable.
The ECM20 itself requires no driver support, although motherboards and operating systems will still need drivers for the SSDs onboard (like NVMe support). No power connectors are needed, either, and the card can accept M.2 SSDs up to 80 mm in length. SilverStone also provides a low-profile bracket for smaller PCs. There's no official pricing information or a release date yet, unfortunately.