Yes! Its possible and simple..
You can even open your facebook and yahoomail at sametime and chat with your online friends, you can even be chating with two or more online contacts using this service..
Go to http://m.ebuddy.com and login your facebook and yahoo username and password,you can choose to open only your facebook account or yahoo account or gmail account, the choice is yours..
Input your login details and follow the instruction..
Remember its http://m.ebuddy.com