I live in an older home with poor insulation that takes about an hour to cool down a single degree (F); thus cooling the bedroom from 80 to 74 by bed time isn't currently a possibility. So I built an air booster!
Prices for commercial items average about 70 bucks - I scavenged all the parts, so the cost was really just the sugru.
Materials included: Two 120mm fans (old computer cooling fans), a 12v power adapter capable of at least 0.7 amps, and a packet of sugru.
Step 1: Solder Fans Together
Strip the black and red wires on both fans and the power supply and solder them in parallel (red to red and black to black), then cover the exposed wire in heat shrink.
Step 2: Apply Sugru
Apply sugru to the corners and the middle of the fans to reduce vibration on our metal air registers.
Wait a day for the sugru to set and enjoy!