The system additions recommended to review:
•   "Add This" toolbar setting (not in add-ons list)
•   Editable "Similar Items" table at product pages (not in add-ons list)

List of Addons

• Cascading Menus (RTML or DHTML)
• Top/Bottom Editable Menu
• Home Page Table with "Bestsellers"
• Table with "Related Items"
• "Structured" Type of Listing Page
• Order-Ready Listing Page
• Home Page Dynamic Content Rotator
• Pagination of Listing Pages
• Multi-Line Breadcrumbs
• "Shop by ... " Select Box
• Editable Text/Image Page Spots
• "Tell a Friend" Form
• "Opt-In" List
• Hierarchical Site Map
• Custom .CSV Data Export
• SEO-Related Page Settings
• Multi-Type Item Options
• "Currently Viewed Items" Table
• Image Enlarging (AJAX Lightbox)
• Multiple Insets
• "More Info" Pop-Up Layer (AJAX)
• Custom "Availability" Text Field
• Quantity Box for "Order" Button
• Item Discount Calculation
• Item Total Price by Selected Options
• Item Total Price by Quantity Input
• Enhanced Accessories at the Product Page
• "Back-Up-Next" Item Page Links
• "Cross-Selling" Table Style Enhancement
• Items "Back in Stock" Auto Notification
• Floating Shopping Cart Customization or Custom Development
• Style Customization of Checkout Pages