Is there a free type library kind of implementation available for XNA? I wish to use it on WP7, so it should be a managed code. I know can alternatively use spritefont, but I wish to know if other implementations exist for complex requirements.
The nuclex library has more than one font renderer.
Developer's blog, article discussing why XNA 4 fonts don't render as well as they could with spritebatch, with before and after comparisons of Nuclex font rendering vs Spritebatch in XNA4.
Nuclex Vector fonts (very useful for large fonts or fonts that need to be drawn well in 3D).
XNA 4 uses DXT compression on it's font textures, which causes the edges of fonts to be a little uglier than they need to be. XNA also has no Vector font implementation, which Nuclex does.
The nuclex font source code can be found here: https://devel.nuclex.org/framework/svn/graphics/fonts/