SIP to Skype & vice-versa

Evenin all

Quick question or two. Do Skype users have a number I can dial from my SIP phone? (VoIPtalk)

Or do they have to get Skype-In or whatever it's called? (Which kinda defeats the purpose, as then I have to call their Skype geographical number - meaning I have to pay, so I may as well call their real landline instead! Rather than a geographical number, can Skype users opt for a VoIP phone number instead?)

Finally, can they phone my 8 digit VoIP number for free? (If not free, I would greatly appreciate it if anyone knows the charges).

Thanks in advance, Ben
(I trawled through Skype's website a while ago, but couldn't find the specific answers I was looking for).

I would start from the assumption that there is zero interoperability between Skype and SIP.

Someone may have built a SIP <-> Skype gateway but such things are not in common use.

Skype runs its own protocol so it doesn't work with other networks...

Thanks for the heads-up guys. I feared that was the case

Balls. I'm just gonna have to threaten some friends into getting a proper VoIP provider