Подскажите варианты использования «железок»
Да просто море вариантов использования, зависит от того, чем вам интересно заниматься. Вот, например, для Raspberry Pi:

Webcam server
Vehicle tracking (using an add-on GPS module)
Streaming internet radio box
Vehicle Diagnostics, full OBDII logger with touch screen interface
Baby monitor
Media server by adding a couple of USB hard drives
Media receiver (hopefully we’ll get a port of XBMC or PLEX)
Video chat
Game emulator, running MAME (build your own arcade cabinet?)
Network Attached Storage setup (NAS)
Mini web server
FTP server
Proxy server
Firewall
Portable Media PC
Run an alarm system
Security webcam (with motion sensor)
Control garden lighting
Control sprinkler system
Wearable computer
HTPC for TV web browsing
HTPC for streaming Netfilx / Hulu etc
In car Computer
Thin client computer
Game server
IRC / chat server
build a cheap laptop
build a cheap tablet
create a digital photo frame
Asterisk VOIP server
PBX
Home automation system
MP3 player
Portable personal computer, you can use it anywhere you can find a monitor.
multitouch screen coffee table
Wall hanging screen with voice control for network pictures, weather, news and RSS feeds
Cyber Cafe computer
Video conferencing system
Personal weather station / logger
Control a light display
Control an LED board
Put it in an old mac classic or mac plus case as a general purpose computer
Intelligent photo frame with touch
Wardriving setup
A dedicated Synth, possibly with touch screen
Solar powered desktop computer
CNC controller
High tech birthday / Xmas presents
Backup server
RSS ticker
High tech alarm clock
Mini projector
DOSBox for games
Processing farm for SETI@Home
Cafe media player
Brains for Arduino setup
Mumble server
Industrial manufacturing controller
TOR server
BitTorrent seedbox
Family notice board
CD / DVD ripping device
Car black box with video
Wall mounted, interactive mood lamp
Robotic telescope / camera controller
Display photographer portfolio images
BitTorrent client
SMS gateway
жирный плюс и ОГРОМНОЕ спасибо! (за ссылку отдельное спасибо)