To me, one of the most annoying things about the current iMac is the location of the USB ports and SD card reader. To plug any USB device into the iMac, you have to reach around to the back of the device and the same is true for the SD card reader. Satechi's Aluminum USB 3.0 Hub + Card Reader (US$29.99) brings those ports out to the front of the iMac where they're easily accessible.
The Hub + Card Reader features three USB 3.0 Type-A ports supporting data rates up to 5.0 Gbps as well as SD and micro SD card slots. The latter is very welcome, particularly since I can never find my micro SD card adapter. The device comes with an 11-inch cable; I found that length to be perfect for placing the Hub + Card Reader on the iMac's "foot".
Like many of Satechi's other Aluminum line of accessories, the USB 3.0 Hub + Card Reader matches the standard aluminum finish of the iMac quite well. Of course, the device can be used with Macs other than the iMac, but it seems particularly well matched to the all-in-one.
There are less-expensive combo hub and card readers available, but my experiences with Satechi's products have been excellent so the extra $10 or so that you'd spend on the Hub + Card Reader is worth it. I'm just happy that I no longer need to stand up and look at the back of the iMac to read an SD card or plug in a USB cable.