A Western Digital Green 240 GB SATA SSD (WDS240G2G0A) for under 36€, for use with my headless Odroid HC1 (single-board octa-core Exynos5422).
I also have a USB-miniPCIe/WWAN adapter and a Huawei ME909s-120 3G/4G/LTE modem with a 9 dBi passive antenna to use with that, to make it into a firewall/router/miniserver for local cameras. In a Beginner thread, I also mentioned I'm working on an Teensy 3.2 microcontroller carrier, to be used for a small custom display (OLED or IPS TFT) and a couple of buttons, power control, and checking for voltage/current spikes or dropouts; and for serial console via Teensy's USB connector. (Getting all working at the same time does require changes to the Samsung serial driver in the Linux kernel, though.)
I likey.