Extensions and add-ons can greatly enhance the functionality of ArcView 3x and ArcInfo 7x. Many of these extensions can be found for free on the internet. Use this page as a great starting point for your search.

ArcView Recreation Symbology
This extension was created to support the display of commonly used recreation symbols in ArcView.

The Unofficial ArcView Symbol Page
Symbols, fonts and icons for ArcView and ArcInfo.

ShapeShifter
Shape Shifter is a stand-alone utility which helps you identify the associations of shapefiles and ArcView GIS projects.