About 8 or 9 years ago, my company had switched one of our clients to a new ISP, and we were given a 1-800 support number. Well, the first support issue came up, and I dialed the number - only to be greeted by a pleasant female voice that assured me it was looking for a support technician. After our issue had been resolved, I asked the support tech what was with the digital secretary - mind you this was well before the age of taking to IVR systems and voice mail hell. He explained to me that he was using a service called Wildfire. Wildfire and other similar services would offer people a single number that would route all of their incoming calls using pre-defined rules. It could send calls during business hours to your desk phone, calls after hours to your cell, etc. It could also consecutively ring different phones until it found you.
Unfortunately, a lot of these services didn't quite make it, primarily because they were before their time. However, lately I've been playing with a similar service from GrandCentral (now owned by Google) GrandCentral offers me a lot of the services of Wildfire and company for free! (Okay, in classic Google fashion, its a beta, and will be free during the beta period, and I am not so sure how much it will cost when it goes 'live' but I will milk it for now).
With GrandCentral, I get to pick a phone number, and give it out to friends and family. I then can re-direct my incoming calls based on who's calling me. I can also switch phones in middle of a call - for example, if you call me on my GrandCentral #, and I pick up on my cell phone. I can switch it to my home or desk phone seemlessly!
I can also record calls, screen calls, and even screen voicemails - i.e. I can listen to a caller while they're leaving me a voicemail and jump into the call if I need to.
Want to try it - there is a button on the side of this page that will let you give me a call using GrandCentral, try it and leave me a message!