There are a few very good programs around that I like to link with a short description of what they do.
There are a lot more tools around but those are more for creators and advanced user
Any Game Starter 3 by Johna
This tool lets you have multiple profiles of your game. For example you can have different languages or you can have one game with medieval stuff, one with pirate stuff and one with all your downloads. Anything that is normally stored in your user file folder can be different for ever Any Game Profile you have. You can even decide which EPs you want installed.
CC Magic by granthes
Custard by Delphy
This tool lets you have control over the Sims3Packs you install into your game. For a tutorial on how to use this tool, see Delphy’s Custard
Create your own no effects mod tool by velocitygrass
A tool which lets you create a mod that lets you decide which effects you want hidden. The mod you create needs updating with every EP-patch.
No (or fewer) automatic memories by velocitygrass
A tool to make a mod in which you decide which memories are worth making.
Sims 3 Dashboard tool by Delphy
This tool helps you detect faulty Package files, fixes them if possible or lets you get rid of them. For a tutorial on how to use this tool, see Delphy’s Dashboard.
SimsReadmeGenerator by ChocoChipSim/Andu
Lets you create a Readme file for your uploads. What cc/Store and EP content did you use ?
The Sims 3 Crash Log Analyzer by FordGT90Concept
This tool analyzes the crash logs your game creates when you experience a CTD. It tells you the possible causes of your crash and has some suggestions on how to get rid of them. If you get an unknown error you can post your crash log the comments of the tool and maybe Ford has a solution for you.
Sims3Pack File Generate Tool by Sakura4
Convert package files into Sims3Packs
Sims3Pack Multi-Extracter by Delphy
This tool lets you extract the package files that are inside a sims3pack.
The Sims 3 Patch Downloader by FordGT90Concept
Let’s you download those patches without all the hassle the Launcher provides. Also patches ALL your games and not just the base game and your newest expansion pack.