If you own an iMac, you know that it's hard to reach the USB ports. Enter the ExoHub, which my compadre, Steve, really likes (he has a prototype).
There’s a Kickstarter campaign to fund “The Hub Apple Should Have Made.” However, they're way under their goal and could use your support if the product sounds promising to you.
The ExoHub is compatible with all 3.0 USB ports and it can work without a power adapter. You can connect your iMac to the hub in three steps. Once connected, you have get access to four USB 3.0 ports, one rapid charger, and an SDXC card slot.