I use DefScape. It comes in 3 different resolutions, to suit people no matter the speed of their computer. It is also regularly updated, has random mobs support [GLSL shader too, but I don't use it] and looks pretty damn awesome. Most texture packs that try to make Minecraft appear 'Smoother' just end up making it look like a cartoon. This texture pack manages to make Minecraft smoother without that.
DefScape