I just bought a used Pantech Burst (also called Presto, and P9070) Android phone for US$50, from craigslist. It has a dual-processor Snapdragon ARM7, 1GB RAM, 16GB flash, and a microSD slot. It was running ICS until I replaced that with (Slim's unofficial port of) Cyanogenmod 10. These can be had easily for well under US$100 on ebay, making it the best value I know of in a smartphone. The batteries are supposed to run out a little faster than some other phones, but you can get a pile of spares, and a busted phone to charge them with, very cheap.
I also bought a Wandboard, a 4.5-inch-square complete computer system with dual ARM, 1G RAM, USB (both host and gadget), GigE, 2 microSD slots, SATA, WiFi, Bluetooth, optical and analog audio, HDMI, camera connector, serial, JTAG, and an expansion header, that burns <2W, for $100. A handsome case is another $10. They provide Android Jelly Bean and Ubuntu boot images. This seems like a better value than a RasPi, Mele, or Beagle. Since I bought it they have added a quad CPU version with 2GB RAM for $20 more.
I bought a used Netgear WNDR3700 wifi router for $40. It had the buggy 220.127.116.11 firmware that refuses to load the (less buggy) 18.104.22.168 update. There are lots of these out there because they all automatically downloaded and flashed the bad firmware. I used tftp to downgrade it to 22.214.171.124 (got directly from Netgear), and then installed DD-WRT on it. It has plenty of flash and RAM, and a USB socket.
I also bought a used Cisco/Linksys EA2700 wifi router, also for $40. These are cheap now despite excellent features (agbn, 64M RAM, 64M flash) because the Cisco firmware in them has turned out to be easy to crack remotely, but now it can run DD-WRT.