I've mentioned Skype before, and things just get better and better with this service. Around three weeks ago I took out the 30euro option to get on the beta of SkypeIn/answer service. This gives me an ordinary London based telephone number which will divert to any location that I am logged into Skype. If I'm not logged into Skype then the call gets directed to an answer service and they get the option to leave a message (this is also the case for normal Skype calls to).
All in all I've found it great - I work in several locations at the moment and have been experimenting with it. Most of the people I work with directly already use Skype so for them calls to me are free, those who don't now have the option of either my mobile number or the SkypeIn number - in terms of costs SkypeIn is *much* cheaper (local or national rates) than calling my mobile provider.
The only minor niggle I have is that you cannot tell if you have a voicemail left for you from the Skype website. The ability to listen to these messages from just a web-browser would be helpful in certain circumstances.
Over the next few weeks, I'm going to be doing a fair amount of traveling including the US (JavaOne here I come) some time in Germany, and hopefully some time in Brussels if a new contract comes off. I'll report back on how SkypeIn works for this - in theory the savings should be huge.