Ghostscripter seems to be the main competitor to Associate-o-Matic. For hardcore coders, this script offers the benefit of providing the source code so that customized coding changes can be made. (AOM code is encrypted.) Ghostscripter seems to have a lot of loyal followers at the Digitlapoint forums. Here’s a summary of features:

Built-in shopping cart allows customers to add their product to the cart and
leave your website only when ready to checkout at Amazon.com
Amazon XML pages cached to speed up loading times
Product information retrieved via XML
All pages are easily modified via the built in WYSIWYG editor (i.e. 6+)
Have mutiple templates installed, insantly changeable through the admin panel.
Optional Newsletter system
Optional Dynamic Title, Sort Box, Meta Keywords and Path bar
Automated Error reporting to your email
Custom Categories & Products
Random Hot Deals & Featured Items.
Automatic DB fill for Hot Deals & Featured Items.
Supports US, UK, DE, CA, FR and JP
All languages in language files for easy change
Powerful Admin Panel
Optional mod_rewrite for search engine friendly urls
5 Templates for your to choice from.
1 Year of Updates/Fixes
1 Year of Technical Support
Amazon Shop Minimum Requirements – MySQL and php 4

Features:
• Free (as in beer) – Open Source GPL license (as in freedom).
• Easy – put your associate id in the script and your affiliate store is fully stocked and ready to run.
• Simple – the script only requires that Perl be installed on your server.
• Cross-platform – versions of this script are known to be running on both Linux/Apache and Windows/IIS.
• Flexible – control the operation of the script through how you link to it.
• Customizable – change the look and feel of the results through simple HTML template files.
• Established – thousands of web sites are currently running their own Web store with this script.
• Multi-lingual – change the language by editing a simple text file. Currently known to be running on sites in German, Spanish, Japanese, and Estonian.
• Multi-national – works with Amazon.com, Amazon.co.uk, Amazon.de, Amazon.jp, Amazon.ca, and Amazon.fr.
• Scalable – change a single setting to increase or decrease the cache size to trade between speed and disk space.
• Promotional – all of the searches are automatically cross linked throughout the results for suggestive selling.
• Efficient – many users have remarked how this script returns results faster then shopping directly at Amazon. Now it’s even faster with cached results and prices that are updated hourly.
• Extensive – many ways to list the products you want. Browse all products, list selected products by ASIN, or search by many different methods. Even search for third party products by condition and ASIN or by seller.
• Reliable – the script has been programmed to not make any sales if it cannot find an Associate ID. So that we have done our best to ensure that you get credit for every sale.
• Safe – no URL input is directly used to access your server. All URL input is sanitized to deter hacking.

Examples:
• You can see the script in action on my site displaying Books on Web Services, my Wishlist, or All Bestselling Products.
• I am not a graphic artist, I’m barely a programmer. So don’t judge the quality of the program by how ugly my HTML is, look at what Other Sites are doing with my script

We’ve seen some nice stores built using this script, but it seems to take quite a lot of coding effort to get it a polished, professional look.

Associate-o-Matic is probably the easiest to use and most popular  Amazon store script available.  The tool lets you build a custom Amazon store with 1000’s of items in minutes. The product can be downloaded and installed on a local server, or it can be run in a hosted mode under a subscription plan.

The newest version of Associate-O-Matic features improved performance and stability, enhanced product listings, access to new Amazon categories, a number of new settings and preferences, and an advanced search capability.

Absolutely NO programming required
Absolutely NO database required
You keep 100% of affiliate traffic (referral commissions) from your website/store **
Additional categories in addition to the new ones added above include: Books, Music, DVD, VHS, Electronics, Kitchen, Software, PC/Video Games, Magazines, Toys, Camera/Photo, Baby, Computers, Tools/Hardware (categories will vary by locale)
Sell 1000’s of items from Amazon and the Amazon Marketplace
Can be installed on multiple servers, with an unlimited number of domains, so long as the Amazon Associate IDs you setup inside Associate-O-Matic are registered to you.
Utilizes Amazon’s Quick-Click technology which gives your visitors the option of either adding an item to their Amazon shopping cart or, if they are recognized customers, buying the item with Amazon’s 1-Click® technology.
Uses your existing domain name (i.e. http://www.yoursite.com/shop.php)
Completely customizable to the look and feel of your existing website (colors, fonts, etc…)
Supports linking to existing HTML pages (i.e. contact page, company page, etc.)
Supports any custom HTML content you provide such as Rotating Ads, Featured Items, Newsletter Subscription boxes, etc.
Searching by keyword and category
Supports third-party site traffic tracking programs
Dynamic titles and meta keywords/descriptions for search engine friendliness
Simple, yet powerful, browser-based control panel
Page caching for faster page loads and less network traffic AVAILABLE TO LITE USERS SINCE v2.5
Version checker inside Control Panel
Cross-browser compatible (Microsoft Internet Explorer, Mozilla FireFox, Opera, etc…)
Powered by PHP together with Amazon.com E-Commerce Service (ECS v4.0) technology

Both free and paid versions of the script are available.