Since I live in Switzerland it could be appropriate to have a Swiss landline number, not only at work but only at home or wherever I am (since it is connected via our mobiles).
Sipcall.ch has a good offer where they offer landline numbers for free and only charge for outgoing calls. Since Android 3.2.2 there is native support in Android and for iOS there are good (and free) clients available and I have found the one from 3CS working well for me.
So, for those who wants to call, the landline number is +41325123044 and the sip address is sip:41325123044@free1.voipgateway.org.
My Swedish landline number (via Skype) is still +46317995551.
Other phone related blog entries.