Orkut, the social networking site from Google has its popularity in India and Brazil only. But recently Facebook had gone past the number of users for Orkut. Now Facebook is offering integration of Orkut for Indian users. If you have recently logged into Facebook, you can see a message displaying search Orkut friends in Facebook. You just need to sign into your Orkut account and then Facebook will import all the contacts.
Once you authorize access to your Google account, you can import all your friends and then Facebook tells you who all are available in Facebook. You can easily add them to Facebook by sending an friend request.
Apart from this, for friends who are not on Facebook, but only on Orkut, you can send an invite asking them to join Facebook. This could prove costly for Orkut which is already hit by lot of issues including viruses and script attacks.