MasterController.
I provide instructions for installing them on my blog. It's an adapted version of the ones Jeana posted in this board.
1. Navigate to Documents > Electronic Arts > The Sims 3.
2. Create a New Folder. Name it “Mods”. It must be capitalized.
3. Enter that folder and create a new Subfolder – call it “Packages” (again, capitalized)
4. Now we need a specific file. Download
this file (direct download) and place it in your Mods folder.
5. Now all that is left is… Downloading a Mod! Please note that the following instructions work if you are using Windows 7. If not, you may need to download a program like 7-Zip or WinZip.
6. Download the Zip file from the site. If you download from NRaas Industries, it will have little link at the bottom.
7. Put it somewhere safe, like the Desktop.
8. Extract it. Right Click it and choose “Extract…”. Press OK when prompted. If you do not see this option, try again. If you still don’t, download a program like I explained in Step 5.
9. Copy the one file inside into your Packages folder.
10. You’re done! Enter the game.