Yup, just do it. My version might be hopefully very optimized, but it works. Here is one directional light and multiple point lights:

http://dl.dropboxusercontent.com/u/45638513/02_01.png

I managed to cut down on shader body implementations with parametrized uniform inputs for the pixel shader. You can have theoretically an unlimited number of lights, but after a fair number of pixels affected by the lights and overall objects illuminated, performance drops down quickly. But it is enough for most realistic lighting schemes.