If you're a music maker who wants to connect an XLR microphone or mixer to an iPhone, a Mac, or an Android tablet, you can do so easily. All you need is CableJive's $35 ProJive XLR. This cable lets you connect your mic or mixer by way of a 3.5mm microphone input. The cable even sports a headphone jack for connecting a set of headphones or studio monitors to keep track of the audio input. The only hitch here is that the ProJive doesn't support mics that require phantom power (power over the microphone cable).
For many people, a good USB hub is still an essential part of their computer setup--they simply have more USB devices than their computer has ports. A hub is also useful for keeping your desk clear, as you can connect a single USB cable to your computer and run it under or behind your desk, where all your devices are connected to the hub. And, of course, if you're a laptop user, a hub means that you need to disconnect just a single USB cable when you leave, and to reconnect only that cable when you return.
Travel hub: If you need more ports while on the go, look at iLuv's $25 iCB709 4-Port USB Hub. It's a bit pricey, but it offers four USB 2.0 Hi-Speed ports in a bag-friendly package: The hub is just 1.7 by 1.8 by 0.6 inches, and it comes with a 4-inch, shielded USB cable for connecting to your laptop's USB port.
One hub to rule them all: For some of us, four ports aren't nearly enough, especially on our desktop Macs, which play host to various iPhones, iPads, iPods, cameras, printers, thumb drives, and more. Satechi's $40 (currently on sale for $28) UH-12P 12-Port USB Hub generously provides 12 powered (5V, 250mA) USB 2.0 ports. The hub is surprisingly compact, at 8 inches long, 1.3 inches wide, and 0.8 inches thick, arranging eleven of its dozen USB ports in a single-file line; the twelfth is on the end. The eleven top-mounted ports are split into two banks--you can temporarily disable each bank with the flip of a switch.
An included power adapter provides power (a total of 2A) to the ports, and you connect the hub to your computer using the built-in 3-inch USB cable or the included 40-inch extension cable. Satechi also tosses in a strip of 3M adhesive to keep the hub from sliding around on your desk. My biggest complaint about the 12-Port USB Hub is that each port is lit with a bright-blue LED that you can't turn off without disabling the port.