Cardboard

Modding api

Modding api that can be @required in userscript header (no install neccecary)

Recommended
BetterChat

Improved chat bubbles

Antenna

3D Web-based peer to peer voice chat

Recommended
Better Inventory

More items on inventory pages, resizable critter, and sorting

Recommended
Big screen

Game fills entire screen

Recommended
Hi-Res

Fixes blurriness

Critterguration

Settings API that shows each mod's settings in its own tab

Shop ease

Makes shop/chat log opening and closing look nicer

Recommended
Box Critters Texture Pack Manager

This extention lets you easily switch between different themes, add new themes and create new themes.