I was messing around on the forum, and I found some pretty cool mods that work really nice together. One of them is the GLSL Shaders Mod, and I suggest you use Sildur's Shader Pack, because it has the best results with the least lag. By saying this, however, I don't mean you won't get lag. My computer is an i7 with 8gb of RAM, and my Minecraft runs at a maximum of 20 frames per second. Don't fret, though - Optifine to the rescue! If you still get lag, you should try the FpsPlus+ Mod, which is compatible with the former. A few other effects include Blocks3D, which, unlike other "3D blocks" mods, doesn't completely change the way they look, it only renders flat blocks (tall grass, redstone dust, rails, etc.) with a sort of thickness, so it doesn't completely change the look of Minecraft, which I like (and yes, it does work with the wavy grass shaders). Last, but not least, the Animated Player Mod, which replaces the vanilla player model with elbow joints, knee joints, and even a moving mouth, moving eyes, and moving eyebrows!
But now, I'm sure you're asking, "How do I get these to work?", and I have the answer: Forge. Just download the installer, and install, then put all the mods into your mods folder, and put the shader pack into a new folder called "shaders" in your ".minecraft" directory.Also, about that last mod, if you don't feel like going through the process of editing your player skin to get those awesome facial expressions, just send me a private message/email saying what you want (mouth, eyebrows, eyes) as well as the image file of your skin, and I'll modify it to have whatever effects you want, and send it to you.
[EDIT] Also, another cool mod is the Improved First Person Mod. It requires the Render Player API. All you have to do is put those two files into your mods folder, and they will work. Oh, I almost forgot to tell you what they do! Well, the first one changes the way the first person view looks by rendering the whole body, so you don't have just a disembodied arm in your first person view. It doesn't get in the way, though, it just makes it so you can look down and see your body.