Well, an emulator would be a pretty good start ;)

WinUAE is a 32-bit Windows version (XP/Vista/7) of the UAE Amiga Emulator. UAE is the collaborative effort of a number of Amiga enthusiasts to create a portable Amiga emulator.

WinUAE allows you to run Amiga software under Windows, including many games, demos, and applications. General compatibility is excellent, and there are a number of enhancements in WinUAE compared to a standard Amiga computer.

Although not an internal component part of the actual AIAB distribution you wouldn't get far without it, unless of course you own a real Amiga, that's a different story.

Scalos

The original Workbench gets older every day and is being left behind by other desktop systems. Scalos's original author, Stefan Sommerfeld, decided that there had to be something new, and so Scalos was born.

First of all, Scalos is NOT a replacement OS, Scalos integrates a lot of additional functionality and an enhanced look without losing any of the look-and-feel we all love about the real Workbench.

AmiStart
AmiKit

As many other Tools this one is another example of a Windows like Starmenu, unlike most of them you can drag&drop items direct in the menu. Developed by Darius Brewka

DOpus 4
GPSoftware Link - Get DOpus

DirectoryOpus 4 (or 'Diropus', or 'DOpus') is a legendary file manager for Amiga Computers. It features two directory windows, a very intuitive graphical user interface (including Drag'n drop functionality) and is probably one of the most configurable programs you'll ever come across. Developed by Jonathan Potter.

MagicWB
www.sasg.com
MagicWB is a full replacement for the Graphic User Interface of the Workbench and has become the standard visual interface on the Amiga. Over the years.This is the user archive and some features are not customisable unless you register with www.sasg.com.
MUI
www.sasg.com
Needs no introduction. This software is the basis for many Amiga applications. It lets you customise nearly every pixel of an application's interface, incorporates user-friendly controls and has tons of other features. This is the user archive and some features are not customisable unless you register with www.sasg.com.
Ultimate Amiga Description
English Amiga Board Description
AmiBay Description
Aminet Aminet

Aminet is a set of interconnected WWW and FTP servers hosting freely distributable Amiga software. Established in 1992, Aminet belongs to the Internet's oldest software repositories, the total size of the archive has recently crossed the 30 GB barrier.