OptiFine have released a stand alone .jar file that lets you play Minecraft with all the benefits of OptiFine. It is still in test stages so some features are missing but they are being added and worked on.
Start by downloading the appropriate version of OptiFine for your version of Minecraft from this link.
Click on the installer you just downloaded, which will automatically install OptiFine for Minecraft. It will also create a profile in your Minecraft launcher called "Optifine."
Open up your MC launcher and select the Optifine profile.
You'll know that it's working successfully when you see the name of the profile in the Minecraft screen.
For more information, check out the video guide below from SexyPurpleUnicorn: