What can you get with $25? Your very own, cute little Raspberry Pi computer. What can you get with that, plus a little time, a few peripherals and some command-line know-how? Your very own Tor proxy and wireless access point.
Adafruit's got the goods with an instructional on turning a Raspberry Pi into an "Onion Pi" — a terminal loaded with some serious surveillance-vanquishing power. Essentially, Tor protects your privacy by letting you maintain your anonymity. It routes your Web traffic through various relays to conceal your location and identity, and it has been in use by parties legitimate (and not) whenever an incredibly high level of anonymity is needed.
The hardware required is pretty straightforward: You need the Pi computer, Ethernet cable, Wi-Fi adapter with antenna, the Raspbian OS saved on a SD card and a power supply. You can cobble most of that together from various sources — you might even have some of it lying around — or you could buy an Onion Pi Pack from Adafruit for $94.95. (A portion of the sales will be donated to the Tor Foundation.)
Users install Tor via the command line, edit the host access point (to, say, "Onion Pi") and change the password. A few more commands, an edit to the IP routing tables, and sha-bam — you're routing Wi-Fi connections through Tor. If you want to become an actual part of the network, you can even set up the Pi as a Tor relay.
While some organizations don't take too kindly to people hacking their kit, the Raspberry Pi Foundation seems pleased as punch if people could use this to "Foil the NSA and Prism with a Tor proxy."
If you prefer your security with a little less work, you could always go with something like Disconnect 2.