After over a year in invitation-only Beta, Google Voice has finally gone live. Though it started life as Grand Central, it's grown beyond that. With a Google Voice number, you can direct calls to a "real" phone–office, home, cell, it doesn't really matter–or even send them directly to voicemail. And speaking of voicemail, your messages are automatically transcribed and can be picked up on the website or have them sent to you. When you give out your Google Voice number, you're not giving out the number for a real phone, so you don't have to worry about being stalked by your callers, and for that matter you can set up filters to kill calls from numbers you aren't interested in.
In addition to receiving calls, you can make calls via Google Voice as well. Just enter the number you're calling and pick the phone you want to talk from, and let the magic happen. The call is placed and rings back to your phone. Pick up and you're connected to your destination number. You can also send text messages, although SMS shortcodes aren't supported. Another often-asked-for but not-currently-implemented feature is sending and receiving faxes. Maybe some day.