From Test-Scratch-Wiki
Each modification has its own design goal and reason for creation. Some, such as Snap!, add complex data structures. Others add lots of new blocks. Each provides a unique experience, and aims to change Scratch, for the better.
 Warning: | Do not download Mods unless you're sure they're safe! |
There are also some that allow for more ways of external communication which works with LEGO Mindstorms NXT robots. Mesh is online compatibility which is implemented into some modifications. Others provide a more advanced experience, for more advanced users.
