You can now link both your Google Account (including Gmail) and Yahoo ID with your Facebook profile.
The advantage of linking you other online accounts with Facebook is that if you are signed-in into any of the above services, you’ll automatically be logged into Facebook as well. So for example, if you working in Google Docs or writing scraps in Orkut and then decide to open Facebook in another tab, you won’t see the Facebook sign-in screen anymore.
To set up this association between Facebook and Yahoo/Google Accounts, just go to Facebook -> Accounts Settings and click "Add a new linked account".
Facebook lets you link only one account per web service so choose the ID that you use most frequently on the web.
Related: Managing Multiple Google Accounts