I love the Cube. It's a compact extruded-metal case that houses six blades that hold many Bitcoin mining ASICs on each one. With a fan on one end and a grilled opening on the other, it's easy to cool (see my tip below).
The Cube mines at 30 GH/s using some 200 watts of power, and as of this writing, they're priced at just $119 at JonesGear (plus 5 percent off when you use coupon "MacObserver"). It's also easy to overclock to 38 GH/s, though that bumps power consumption up to 280 watts.
ASICminer Cube - Front and back
Note that you need a separate PC power supply unit (PSU)—if you plan to run more than one Cube, get a PSU with the right number of connectors that supplies enough power for all of them.
Like I said, I love this device. It's stackable, it's well-built, and it only kind of looks like a piece of ugly mining gear. On the down side, it uses an early generation of ASIC, which is why it uses so much power. That ASIC also needs an older form of software that requires you to run Slush's proxy (you can also use BFGminer as a proxy in MacMiner).
I'll be writing up a tutorial on installing Slush's proxy on your Mac another time, but this is command-line world. The easiest thing would be to use BFGminer as a proxy, but when I tried that, I got less performance from the Cube.
Still, it's a good way to start mining for a relatively small investment.
Tip: The fan that the Cube comes with is NOISY. It's LOUD! If that's an issue for you, you can change out the fan, but do so at your own risk as it could void the warranty. I found that the excellent Scythe Gentle Typhoon keeps it cool at a tiny fraction of the noise. It adds to the price, but when you go to sell the Cube, put the old fan back on and keep the Scythe for your next miner.
Next: Step up to the Antminer S1