On Mobiletuts+ there is very good tutorial on Text formatting for Android. Quick Tip: Customize Android Fonts
EDIT: Tested it myself now. Here is the solution. You can use a subfolder called fonts but it must go in the assets folder not the res folder. So
assets/fonts
Also make sure that the font ending I mean the ending of the font file itself is all lower case. In other words it should not be myFont.TTF but myfont.ttf this way must be in lower case