"If your office has a phone system that uses short extensions internally, have your IT department set one up to redirect to your cell phone. That way you can tell your coworkers to dial “5555”, instead of your whole number." Fantastic tip! Super simple but I really think this idea will make you feel more available to your co-workers.
Protip: This can be done extremely cheaply with Asterisk and a SIP provider; it can be done faster at a slightly higher cost with Twilio. EDIT: changed lower to higher @ "cost with Twilio". Need moar coffee.
ring a desk phone for 10 seconds then ring the desk phone and a cellphone for 55 seconds then drop to voicemail voicemail is transcoded to mp3 and emailed to your preferred address as an attachment, along with call ID info.