Twilio is a great service. And as Dana mentions you can create an entirely customized voicemail and phone tree system for your company so that customers who call get an individualized experience.
I recently left Microsoft to go it alone, and my startup SocialKind has built a number of solutions on top of Twilio (TweetToCall.com, EscapeMyDate.com, enterprise solutions in healthcare and finance, etc.). I enjoy working with businesses to build interactive phone solutions connected to the web. If you're looking to do some of this for your business, or just want to chat about Twilio and hack a bit, drop me a note at kevin@socialkind.com or @mistermorrill on Twitter
Happy holidays!