SIPBroker offers free PSTN numbers (here we can call it virtual phone numbers, only here, hehe) in 30 Countries for unlimited voip incoming calls to your IM or voip softphone (covered over 2,000), such as google talk, PSTN numbers are in Asia, Middle East, Europe, North and South America, Australia and New Zealand etc.
Let me tell you how to use it if you don't know: (no registration needed)
1. Check here and see if the free PSTN numbers covered the Country you want to have one or not.
2. Check the SIP-code here of your voice services provider, however, there are just too many voice services provider there, just type the proxy of your voice service provider and see if it is covered by SIPbroker or not, if yes, there will a SIP-code for it. Let me set gtalk2voip （google talk) as an example:
I am not sure if it is in the list of SIP-code, so I search here:
so you will get the result by scroll down at the same page:
It is showing that the SIP-code for Gtalk2Voip is *018
3. Now go to your gtalk to check your check your SIP-code in Gtalk2voip number which is used as an extension of the PSTN number you chose:
login your gtalk, and add email@example.com as friend, and then send a message HELP, and you will see messages back with a blue link to your Gtalk2voip, click it and you will see "your SIPBroker ID is: *0182118644" in red on the left of the page (I give mine for example)
This is the your own SIP-code (extension number of PSTN).
4. Now call the PSTN you chose, when prompt, enter *0182118644 and your gtalk will ring. (make sure enter the "*" it is part of the numbers)
Now you have a PSTN (or you can say it is virtual phone number) for your gtalk.
Other voice service providers, if it is in the list of SIP-code, will give you your own SIP-code after sign up.