We have a team member in a different country, and are trying to figure out the most viable option to provide them with access to our Team Foundation Server for Visual Studio 2010.
If they are part of your corporate LAN/WAN, they should be able to get access just like a local user. If they are external, you have a couple choices:
VPN: You could give them VPN access into your network, then they could access like a local user.
Expose: You could expose TFS to the outside world by allowing the appropriate ports through your firewall.
You can also take a look at the TFS Proxy, but honestly I haven't done anything with that yet.
You can check this http://msdn.microsoft.com/en-us/library/bb668967.aspx
Open up port 8080 and route that port to the appropriate server. You can also setup to use HTTPS.
When the remote user is not on the same domain, he gets prompted for the credentials. The remote user can use the Windows Credential Cache (Stored Usernames and passwords for Windows XP).