Connectify
This very nifty piece of free software lets you turn a Windows 7 PC (it only works with Windows 7) into a Wi-Fi hot spot that can be used by nearby devices -- your smartphone, for example, or devices that your co-workers are using in the same location.
The PC on which you install it will, of course, need to be connected to the Internet itself and have Wi-Fi capability so it can provide access to other devices. The computer doesn't necessarily need a wired connection to the Internet (although it won't hurt to have one); its Wi-Fi card can perform double-duty as Wi-Fi signal receiver and transmitter.
Setting up a hot spot is simple: Once you have a connection, run Connectify on your PC and give your hot spot a name and password. Your computer's Wi-Fi card will begin broadcasting a Wi-Fi signal that other devices can connect to, in the same way they can connect to any other hot spot. (Your PC card will broadcast in whatever Wi-Fi protocol it was built for. It also should support devices that use earlier protocols -- for example, an 802.11n signal should allow 802.11b/g/n devices to connect.)
Since your hot spot is password-protected, only people who know the password can use it; the signal is secured with WPA2-PSK encryption.
You can even use Connectify to set up a local network without an external Internet connection. Run it as a hot spot, and nearby devices can connect to each other in a network, even though there's no Internet access. You can use this for sharing files in a workgroup or setting up a network for multiplayer games.
Note that I had problems connecting my Mac to a Windows 7 machine running a Connectify-created hot spot, but I was able to make the connection with other PCs and devices.
Price: Free
Compatible with: Windows 7
Download Connectify